From 2a8ffbe9d71052743e735d866a36e9c92ccf9eef Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Sat, 27 Jul 2024 20:12:49 +0200
Subject: [PATCH] =?UTF-8?q?cs:=20add=20=C2=AB2976.=20Minimum=20Cost=20to?=
 =?UTF-8?q?=20Convert=20String=20I=C2=BB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 cs/minimum-cost-to-convert-string-i.cs | 56 ++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 cs/minimum-cost-to-convert-string-i.cs

diff --git a/cs/minimum-cost-to-convert-string-i.cs b/cs/minimum-cost-to-convert-string-i.cs
new file mode 100644
index 0000000..d8de4ed
--- /dev/null
+++ b/cs/minimum-cost-to-convert-string-i.cs
@@ -0,0 +1,56 @@
+public class Solution {
+    private readonly int UNREACHABLE = 1_000_000_007;
+    private readonly int LETTERS = 26;
+
+    private void FloydWarshall(int n, int[,] distances) {
+        for (int k = 0; k < n; ++k) {
+            for (int i = 0; i < n; ++i) {
+                for (int j = 0; j < n; ++j) {
+                    distances[i, j] = Math.Min(
+                        distances[i, j],
+                        distances[i, k] + distances[k, j]
+                    );
+                }
+            }
+        }
+    }
+
+    private int[,] ConstructGraph(char[] original, char[] changed, int[] costs) {
+        var distances = new int[LETTERS, LETTERS];
+
+        // Everything's unreachable
+        for (var i = LETTERS * LETTERS - 1; i >= 0; --i) {
+            distances[i / LETTERS, i % LETTERS] = UNREACHABLE;
+        }
+
+        // Go through the possible changes
+        for (var i = 0; i < original.length; ++i) {
+            var (u, v, cost) = (original[i] - 'a', changed[i] - 'a', costs[i]);
+            distances[u, v] = Math.Min(distances[u, v], cost);
+        }
+
+        // Handle self-loops
+        for (var i = 0; i < LETTERS; ++i) {
+            distances[i, i] = 0;
+        }
+
+        return distances;
+    }
+
+    public long MinimumCost(string source, string target, char[] original, char[] changed, int[] cost) {
+        var graph = ConstructGraph(original, changed, cost);
+        FloydWarshall(LETTERS, graph);
+
+        var minCost = 0;
+        for (int i = 0; i < source.Length; ++i) {
+            var operationCost = graph[source[i] - 'a', target[i] - 'a'];
+            if (operationCost == UNREACHABLE) {
+                return -1;
+            }
+
+            minCost += operationCost;
+        }
+
+        return minCost;
+    }
+}