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< title data-rh = "true" > Distance boundaries from BFS tree on undirected graphs | mf< / title > < meta data-rh = "true" name = "viewport" content = "width=device-width,initial-scale=1" > < meta data-rh = "true" name = "twitter:card" content = "summary_large_image" > < meta data-rh = "true" property = "og:url" content = "https://blog.mfocko.xyz/algorithms/graphs/bfs-tree/" > < meta data-rh = "true" property = "og:locale" content = "en" > < meta data-rh = "true" name = "docusaurus_locale" content = "en" > < meta data-rh = "true" name = "docsearch:language" content = "en" > < meta data-rh = "true" name = "docusaurus_version" content = "current" > < meta data-rh = "true" name = "docusaurus_tag" content = "docs-algorithms-current" > < meta data-rh = "true" name = "docsearch:version" content = "current" > < meta data-rh = "true" name = "docsearch:docusaurus_tag" content = "docs-algorithms-current" > < meta data-rh = "true" property = "og:title" content = "Distance boundaries from BFS tree on undirected graphs | mf" > < meta data-rh = "true" name = "description" content = "Short explanation of distance boundaries deduced from a BFS tree .
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< p > As we have talked on the seminar, if we construct from some vertex < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > u< / mi > < / mrow > < annotation encoding = "application/x-tex" > u< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.4306em" > < / span > < span class = "mord mathnormal" > u< / span > < / span > < / span > < / span > BFS tree on an undirected graph, we can obtain:< / p >
< ul >
< li > lower bound of length of the shortest path between 2 vertices from the < em > height difference< / em > < / li >
< li > upper bound of length of the shortest path between 2 vertices from the < em > path through the root< / em > < / li >
< / ul >
< h2 class = "anchor anchorWithStickyNavbar_LWe7" id = "lower-bound" > Lower bound< a href = "#lower-bound" class = "hash-link" aria-label = "Direct link to Lower bound" title = "Direct link to Lower bound" > < / a > < / h2 >
< p > Consider the following graph:< / p >
< p > < img loading = "lazy" src = "data:image/svg+xml;base64,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
< img loading = "lazy" src = "data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiIHN0YW5kYWxvbmU9Im5vIj8+CjwhRE9DVFlQRSBzdmcgUFVCTElDICItLy9XM0MvL0RURCBTVkcgMS4xLy9FTiIKICJodHRwOi8vd3d3LnczLm9yZy9HcmFwaGljcy9TVkcvMS4xL0RURC9zdmcxMS5kdGQiPgo8IS0tIEdlbmVyYXRlZCBieSBncmFwaHZpeiB2ZXJzaW9uIDIuNDMuMCAoMCkKIC0tPgo8IS0tIFRpdGxlOiAlMyBQYWdlczogMSAtLT4KPHN2ZyB3aWR0aD0iMTg5cHQiIGhlaWdodD0iNDA0cHQiCiB2aWV3Qm94PSIwLjAwIDAuMDAgMTg5LjAwIDQwNC4wMCIgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIiB4bWxuczp4bGluaz0iaHR0cDovL3d3dy53My5vcmcvMTk5OS94bGluayI+CjxnIGlkPSJncmFwaDAiIGNsYXNzPSJncmFwaCIgdHJhbnNmb3JtPSJzY2FsZSgxIDEpIHJvdGF0ZSgwKSB0cmFuc2xhdGUoNCA0MDApIj4KPHRpdGxlPiUzPC90aXRsZT4KPHBvbHlnb24gZmlsbD0iIzFiMWIxZCIgc3Ryb2tlPSJ0cmFuc3BhcmVudCIgcG9pbnRzPSItNCw0IC00LC00MDAgMTg1LC00MDAgMTg1LDQgLTQsNCIvPgo8IS0tIGEgLS0+CjxnIGlkPSJub2RlMSIgY2xhc3M9Im5vZGUiPgo8dGl0bGU+YTwvdGl0bGU+CjxlbGxpcHNlIGZpbGw9Im5vbmUiIHN0cm9rZT0id2hpdGUiIGN4PSIxMjYiIGN5PSItMzc4IiByeD0iMjciIHJ5PSIxOCIvPgo8dGV4dCB0ZXh0LWFuY2hvcj0ibWlkZGxlIiB4PSIxMjYiIHk9Ii0zNzQuMyIgZm9udC1mYW1pbHk9IidDYXNjYWRpYSBDb2RlIFBMJywgJ0pldEJyYWlucyBNb25vJywgJ0lvc2V2a2EnLCAnRmlyYSBDb2RlJywgJ0hhY2snLCBtb25vc3BhY2UiIGZvbnQtc2l6ZT0iMTQuMDAiIGZpbGw9IndoaXRlIj5hPC90ZXh0Pgo8L2c+CjwhLS0gYyAtLT4KPGcgaWQ9Im5vZGUyIiBjbGFzcz0ibm9kZSI+Cjx0aXRsZT5jPC90aXRsZT4KPGVsbGlwc2UgZmlsbD0ibm9uZSIgc3Ryb2tlPSJ3aGl0ZSIgY3g9Ijk5IiBjeT0iLTMwNiIgcng9IjI3IiByeT0iMTgiLz4KPHRleHQgdGV4dC1hbmNob3I9Im1pZGRsZSIgeD0iOTkiIHk9Ii0zMDIuMyIgZm9udC1mYW1pbHk9IidDYXNjYWRpYSBDb2RlIFBMJywgJ0pldEJyYWlucyBNb25vJywgJ0lvc2V2a2EnLCAnRmlyYSBDb2RlJywgJ0hhY2snLCBtb25vc3BhY2UiIGZvbnQtc2l6ZT0iMTQuMDAiIGZpbGw9IndoaXRlIj5jPC90ZXh0Pgo8L2c+CjwhLS0gYSYjNDU7JiM0NTtjIC0tPgo8ZyBpZD0iZWRnZTEiIGNsYXNzPSJlZGdlIj4KPHRpdGxlPmEmIzQ1OyYjNDU7YzwvdGl0bGU+CjxwYXRoIGZpbGw9Im5vbmUiIHN0cm9rZT0id2hpdGUiIGQ9Ik0xMTkuNiwtMzYwLjQxQzExNS4zNiwtMzQ5LjQxIDEwOS44MSwtMzM1LjAzIDEwNS41NCwtMzIzLjk2Ii8+CjwvZz4KPCEtLSBlIC0tPgo8ZyBpZD0ibm9kZTMiIGNsYXNzPSJub2RlIj4KPHRpdGxlPmU8L3RpdGxlPgo8ZWxsaXBzZSBmaWxsPSJub25lIiBzdHJva2U9IndoaXRlIiBjeD0iMTU0IiBjeT0iLTE2MiIgcng9IjI3IiByeT0iMTgiLz4KPHRleHQgdGV4dC1hbmNob3I9Im1pZGRsZSIgeD0iMTU0IiB5PSItMTU4LjMiIGZvbnQtZmFtaWx5PSInQ2FzY2FkaWEgQ29kZSBQTCcsICdKZXRCcmFpbnMgTW9ubycsICdJb3NldmthJywgJ0ZpcmEgQ29kZScsICdIYWNrJywgbW9ub3NwYWNlIiBmb250LXNpemU9IjE0LjAwIiBmaWxsPSJ3aGl0ZSI+ZTwvdGV4dD4KPC9nPgo8IS0tIGEmIzQ1OyYjNDU7ZSAtLT4KPGcgaWQ9ImVkZ2UyIiBjbGFzcz0iZWRnZSI+Cjx0aXRsZT5hJiM0NTsmIzQ1O2U8L3RpdGxlPgo8cGF0aCBmaWxsPSJub25lIiBzdHJva2U9IndoaXRlIiBkPSJNMTI5LjE0LC0zNTkuODVDMTMwLjk4LC0zNDkuNDkgMTMzLjI3LC0zMzYuMDEgMTM1LC0zMjQgMTQyLjQ5LC0yNzEuOSAxNDkuMTgsLTIxMC4wMSAxNTIuMjQsLTE4MC40MyIvPgo8L2c+CjwhLS0gaSAtLT4KPGcgaWQ9Im5vZGU0IiBjbGFzcz0ibm9kZSI+Cjx0aXRsZT5pPC90aXRsZT4KPGVsbGlwc2UgZmlsbD0ibm9uZSIgc3Ryb2tlPSJ3aGl0ZSIgY3g9IjI3IiBjeT0iLTIzNCIgcng9IjI3IiByeT0iMTgiLz4KPHRleHQgdGV4dC1hbmNob3I9Im1pZGRsZSIgeD0iMjciIHk9Ii0yMzAuMyIgZm9udC1mYW1pbHk9IidDYXNjYWRpYSBDb2RlIFBMJywgJ0pldEJyYWlucyBNb25vJywgJ0lvc2V2a2EnLCAnRmlyYSBDb2RlJywgJ0hhY2snLCBtb25vc3BhY2UiIGZvbnQtc2l6ZT0iMTQuMDAiIGZpbGw9IndoaXRlIj5pPC90ZXh0Pgo8L2c+CjwhLS0gYyYjNDU7JiM0NTtpIC0tPgo8ZyBpZD0iZWRnZTMiIGNsYXNzPSJlZGdlIj4KPHRpdGxlPmMmIzQ1OyYjNDU7aTwvdGl0bGU+CjxwYXRoIGZpbGw9Im5vbmUiIHN0cm9rZT0id2hpdGUiIGQ9Ik04NC40MywtMjkwLjgzQzcyLjAyLC0yNzguNzcgNTQuMjcsLTI2MS41MSA0MS44LC0yNDkuMzgiLz4KPC9nPgo8IS0tIGIgLS0+CjxnIGlkPSJub2RlNSIgY2xhc3M9Im5vZGUiPgo8dGl0bGU+YjwvdGl0bGU+CjxlbGxpcHNlIGZpbGw9Im5vbmUiIHN0cm9rZT0id2hpdGUiIGN4PSI5OSIgY3k9Ii0yMzQiIHJ4PSIyNyIgcnk9IjE4Ii8+Cjx0ZXh0IHRleHQtYW5jaG9yPSJtaWRkbGUiIHg9Ijk5IiB5PSItMjMwLjMiIGZvbnQtZmFtaWx5PSInQ2FzY2FkaWEgQ29kZSBQTCcsICdKZXRCcmFpbnMgTW9ubycsICdJb3NldmthJywgJ0ZpcmEgQ29kZScsICdIYWNrJywgbW9ub3NwYWNlIiBmb250LXNpemU9IjE0LjAwIiBmaWxsPSJ3aGl0ZSI+YjwvdGV4dD4KPC9nPgo8IS0tIGMmIzQ1OyYjNDU7YiAtLT4KPGcgaWQ9ImVkZ2U0IiBjbGFzcz0iZWRnZSI+Cjx0aXRsZT5jJiM0NTsmIzQ1O2I8L3RpdGxlPgo8cGF0aCBmaWxsPSJub25lIiBzdHJva2U9IndoaXRlIiBkPSJNOTksLTI4Ny43Qzk5LC0yNzYuODUgOTksLTI2Mi45MiA5OSwtMjUyLjEiLz4KPC9nPgo8IS0tIGogLS0+CjxnIGlkPSJub2RlNiIgY2xhc3M9Im5vZGUiPgo8dGl0bGU+ajwvdGl0bGU+CjxlbGxpcHNlIGZpbGw9Im5vbmUiIHN0cm9rZT0id2hpdGUiIGN4PSIxMjYiIGN5PSItMTgiIHJ4PSIyNyIgcnk9IjE4Ii8+Cjx0ZXh0IHRleHQtYW5jaG9yPSJtaWRkbGUi
< p > We run BFS from the vertex < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > a< / mi > < / mrow > < annotation encoding = "application/x-tex" > a< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.4306em" > < / span > < span class = "mord mathnormal" > a< / span > < / span > < / span > < / span > and obtain the following BFS tree:< / p >
< p > < img loading = "lazy" src = "data:image/svg+xml;base64,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
< img loading = "lazy" src = "data:image/svg+xml;base64,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
< p > Let' s consider pair of vertices < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > e< / mi > < / mrow > < annotation encoding = "application/x-tex" > e< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.4306em" > < / span > < span class = "mord mathnormal" > e< / span > < / span > < / span > < / span > and < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > h< / mi > < / mrow > < annotation encoding = "application/x-tex" > h< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6944em" > < / span > < span class = "mord mathnormal" > h< / span > < / span > < / span > < / span > . For them we can safely lay, from the BFS tree, following properties:< / p >
< ul >
< li > lower bound: < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 2< / mn > < / mrow > < annotation encoding = "application/x-tex" > 2< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 2< / span > < / span > < / span > < / span > < / li >
< li > upper bound: < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 4< / mn > < / mrow > < annotation encoding = "application/x-tex" > 4< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 4< / span > < / span > < / span > < / span > < / li >
< / ul >
< p > By having a look at the graph we started from, we can see that we have a path ‹ < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > e< / mi > < mo separator = "true" > ,< / mo > < mi > j< / mi > < mo separator = "true" > ,< / mo > < mi > h< / mi > < / mrow > < annotation encoding = "application/x-tex" > e, j, h< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.8889em;vertical-align:-0.1944em" > < / span > < span class = "mord mathnormal" > e< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" style = "margin-right:0.05724em" > j< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > h< / span > < / span > < / span > < / span > › < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > e< / mi > < / mrow > < annotation encoding = "application/x-tex" > e< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.4306em" > < / span > < span class = "mord mathnormal" > e< / span > < / span > < / span > < / span > to < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > h< / mi > < / mrow > < annotation encoding = "application/x-tex" > h< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6944em" > < / span > < span class = "mord mathnormal" > h< / span > < / span > < / span > < / span > and that is ‹ < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > e< / mi > < mo separator = "true" > ,< / mo > < mi > a< / mi > < mo separator = "true" > ,< / mo > < mi > c< / mi > < mo separator = "true" > ,< / mo > < mi > i< / mi > < mo separator = "true" > ,< / mo > < mi > d< / mi > < mo separator = "true" > ,< / mo > < mi > h< / mi > < / mrow > < annotation encoding = "application/x-tex" > e, a, c, i, d, h< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.8889em;vertical-align:-0.1944em" > < / span > < span class = "mord mathnormal" > e< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > a< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > c< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > i< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > d< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > h< / span > < / span > < / span > < / span > › < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 5< / mn > < / mrow > < annotation encoding = "application/x-tex" > 5< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 5< / span > < / span > < / span > < / span > . Doesn' t this break our statements at the beginning? (< em > I' m leaving that as an exercise ;)< / em > )< / p >
< h2 class = "anchor anchorWithStickyNavbar_LWe7" id = "proof-by-contradiction" > Proof by contradiction< a href = "#proof-by-contradiction" class = "hash-link" aria-label = "Direct link to Proof by contradiction" title = "Direct link to Proof by contradiction" > < / a > < / h2 >
< p > Let' s keep the same graph, but break the lower bound, i.e. I have gotten a lower bound < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 2< / mn > < / mrow > < annotation encoding = "application/x-tex" > 2< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 2< / span > < / span > < / span > < / span > , but “there must be a shorter path”! ;)< / p >
< p > Now the more important question, is there a shorter path in that graph? The answer is no, there' s no shorter path than the one with length < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 2< / mn > < / mrow > < annotation encoding = "application/x-tex" > 2< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 2< / span > < / span > < / span > < / span > . So what can we do about it? We' ll add an edge to have a shorter path. Now we have gotten a lower bound of < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 2< / mn > < / mrow > < annotation encoding = "application/x-tex" > 2< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 2< / span > < / span > < / span > < / span > , which means the only shorter path we can construct has < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mn > 1< / mn > < / mrow > < annotation encoding = "application/x-tex" > 1< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.6444em" > < / span > < span class = "mord" > 1< / span > < / span > < / span > < / span > edge and that is ‹ < span class = "katex" > < span class = "katex-mathml" > < math xmlns = "http://www.w3.org/1998/Math/MathML" > < semantics > < mrow > < mi > e< / mi > < mo separator = "true" > ,< / mo > < mi > h< / mi > < / mrow > < annotation encoding = "application/x-tex" > e, h< / annotation > < / semantics > < / math > < / span > < span class = "katex-html" aria-hidden = "true" > < span class = "base" > < span class = "strut" style = "height:0.8889em;vertical-align:-0.1944em" > < / span > < span class = "mord mathnormal" > e< / span > < span class = "mpunct" > ,< / span > < span class = "mspace" style = "margin-right:0.1667em" > < / span > < span class = "mord mathnormal" > h< / span > < / span > < / span > < / span > › ' s do this!< / p >
< p > < img loading = "lazy" src = "data:image/svg+xml;base64,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
< img loading = "lazy" src = "data:image/svg+xml;base64,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
< p > Okay, so we have a graph that breaks the rule we have laid. However, we need to run BFS to obtain the new BFS tree, since we have changed the graph.< / p >
< div class = "theme-admonition theme-admonition-tip admonition_xJq3 alert alert--success" > < div class = "admonitionHeading_Gvgb" > < span class = "admonitionIcon_Rf37" > < svg viewBox = "0 0 12 16" > < path fill-rule = "evenodd" d = "M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z" > < / path > < / svg > < / span > tip< / div > < div class = "admonitionContent_BuS1" > < p > Do we need to run BFS after < strong > every< / strong > change?< / p > < p > < / p > < / div > < / div >
< p > < img loading = "lazy" src = "data:image/svg+xml;base64,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< p > Oops, we have gotten a new BFS tree, that has a height difference of 1.< / p >
2024-01-03 15:14:53 +01:00
< div class = "theme-admonition theme-admonition-tip admonition_xJq3 alert alert--success" > < div class = "admonitionHeading_Gvgb" > < span class = "admonitionIcon_Rf37" > < svg viewBox = "0 0 12 16" > < path fill-rule = "evenodd" d = "M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z" > < / path > < / svg > < / span > tip< / div > < div class = "admonitionContent_BuS1" > < p > Try to think about a way this can be generalized for shortening of minimal length 3 to minimal length 2 ;)< / p > < / div > < / div > < / div > < footer class = "theme-doc-footer docusaurus-mt-lg" > < div class = "theme-doc-footer-tags-row row margin-bottom--sm" > < div class = "col" > < b > Tags:< / b > < ul class = "tags_jXut padding--none margin-left--sm" > < li class = "tag_QGVx" > < a class = "tag_zVej tagRegular_sFm0" href = "/algorithms/tags/graphs/" > graphs< / a > < / li > < li class = "tag_QGVx" > < a class = "tag_zVej tagRegular_sFm0" href = "/algorithms/tags/bfs/" > bfs< / a > < / li > < / ul > < / div > < / div > < div class = "theme-doc-footer-edit-meta-row row" > < div class = "col" > < a href = "https://github.com/mfocko/blog/tree/main/algorithms/10-graphs/2022-04-30-bfs-tree.md" target = "_blank" rel = "noopener noreferrer" class = "theme-edit-this-page" > < svg fill = "currentColor" height = "20" width = "20" viewBox = "0 0 40 40" class = "iconEdit_Z9Sw" aria-hidden = "true" > < g > < path d = "m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z" > < / path > < / g > < / svg > Edit this page< / a > < / div > < div class = "col lastUpdated_vwxv" > < span class = "theme-last-updated" > Last updated<!-- --> on < b > < time datetime = "2022-04-30T00:00:00.000Z" > Apr 30, 2022< / time > < / b > < / span > < / div > < / div > < / footer > < / article > < nav class = "pagination-nav docusaurus-mt-lg" aria-label = "Docs pages" > < a class = "pagination-nav__link pagination-nav__link--prev" href = "/algorithms/graphs/iterative-and-iterators/" > < div class = "pagination-nav__sublabel" > Previous< / div > < div class = "pagination-nav__label" > Iterative algorithms via iterators< / div > < / a > < a class = "pagination-nav__link pagination-nav__link--next" href = "/algorithms/category/paths-in-graphs/" > < div class = "pagination-nav__sublabel" > Next< / div > < div class = "pagination-nav__label" > Paths in Graphs< / div > < / a > < / nav > < / div > < / div > < div class = "col col--3" > < div class = "tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop" > < ul class = "table-of-contents table-of-contents__left-border" > < li > < a href = "#introduction" class = "table-of-contents__link toc-highlight" > Introduction< / a > < / li > < li > < a href = "#lower-bound" class = "table-of-contents__link toc-highlight" > Lower bound< / a > < / li > < li > < a href = "#proof-by-contradiction" class = "table-of-contents__link toc-highlight" > Proof by contradiction< / a > < / li > < / ul > < / div > < / div > < / div > < / div > < / main > < / div > < / div > < / div > < footer class = "footer footer--dark" > < div class = "container container-fluid" > < div class = "row footer__links" > < div class = "col footer__col" > < div class = "footer__title" > Git< / div > < ul class = "footer__items clean-list" > < li class = "footer__item" > < a href = "https://github.com/mfocko" target = "_blank" rel = "noopener noreferrer" class = "footer__link-item" > GitHub< svg width = "13.5" height = "13.5" aria-hidden = "true" viewBox = "0 0 24 24" class = "iconExternalLink_nPIU" > < path fill = "currentColor" d = "M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z" > < / path > < / svg > < / a > < / li > < li class = "footer__item" > < a href = "https://gitlab.com/mfocko" target = "_blank" rel = "noopener noreferrer" class = "footer__link-item" > GitLab< svg width = "13.5" height = "13.5" aria-hidden = "true" viewBox = "0 0 24 24" class = "iconExternalLink_nPIU" > < path fill = "currentColor" d = "M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z" > < / path > < / svg > < / a > < / li > < li class = "footer__item" > < a href =
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