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+// 1123. Lowest Common Ancestor of Deepest Leaves
+#include "leetcode.h"
+
+/*
+ * given the 'root' of a binary tree, return the lowest common ancestor of its
+ * deepest leaves. recall that the node of a binary tree is a leaf if and only
+ * if it has no children, the depth of the root of the tree is 0. if the depth
+ * of a node is 'd', the depth of each of its children is 'd + 1'. and the
+ * lowest common ancestor of a set 's' is the node 'a' with the largest depth
+ * such that every node in 's' is in the subtree with root 'a'.
+ */
+
+int depth(struct TreeNode *root) {
+ if (!root)
+ return 0;
+ int l = depth(root->left);
+ int r = depth(root->right);
+ return l > r ? l + 1 : r + 1;
+}
+
+struct TreeNode *lcaDeepestLeaves(struct TreeNode *root) {
+ if (!root)
+ return NULL;
+ int l = depth(root->left);
+ int r = depth(root->right);
+ if (l == r)
+ return root;
+ return l > r ? lcaDeepestLeaves(root->left) : lcaDeepestLeaves(root->right);
+}
+
+int main() {
+ int r1i[] = {3, 5, 1, 6, 2, 0, 8, -1, -1, 7, 4}, r2i[] = {1},
+ r3i[] = {0, 1, 3, -1, 2};
+ struct TreeNode *r1 = treenode_build(r1i, ARRAY_SIZE(r1i));
+ struct TreeNode *r2 = treenode_build(r2i, ARRAY_SIZE(r2i));
+ struct TreeNode *r3 = treenode_build(r3i, ARRAY_SIZE(r3i));
+ struct TreeNode *lcadl1 = lcaDeepestLeaves(r1);
+ struct TreeNode *lcadl2 = lcaDeepestLeaves(r2);
+ struct TreeNode *lcadl3 = lcaDeepestLeaves(r3);
+ treenode_print(lcadl1); // expect: 2 7 4
+ printf("\n");
+ treenode_print(lcadl2); // expect: 1
+ printf("\n");
+ treenode_print(lcadl3); // expect: 2
+ printf("\n");
+ treenode_free(r1);
+ treenode_free(r2);
+ treenode_free(r3);
+}