cpp: add «513. Find Bottom Left Tree Value»

Signed-off-by: Matej Focko <mfocko@redhat.com>

cpp/find-bottom-left-tree-value.cpp

@@ -0,0 +1,42 @@
+#include <cassert>
+#include <map>
+#include <optional>
+
+#ifdef _MF_TEST
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode() : val(0), left(nullptr), right(nullptr) {}
+    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+    TreeNode(int x, TreeNode *left, TreeNode *right)
+        : val(x), left(left), right(right) {}
+};
+#endif
+
+class Solution {
+    void find_bottom_left(std::map<int, std::optional<int>> &view, int y,
+                          TreeNode *node) {
+        if (node == nullptr) {
+            return;
+        }
+
+        auto &leftmost = view[y];
+        if (!leftmost.has_value()) {
+            leftmost = std::make_optional(node->val);
+        }
+
+        find_bottom_left(view, y - 1, node->left);
+        find_bottom_left(view, y - 1, node->right);
+    }
+
+  public:
+    int findBottomLeftValue(TreeNode *root) {
+        assert(root != nullptr);
+
+        std::map<int, std::optional<int>> leftview;
+
+        find_bottom_left(leftview, 0, root);
+        return leftview.begin()->second.value();
+    }
+};