1.問題描述

Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children. Example: Given binary tree [3,9,20,null,null,15,7],3/ \9 20/ \15 7 return its minimum depth = 2.來自 <https://leetcode.com/problems/minimum-depth-of-binary-tree/description/>

2.題目分析

找出二叉樹的最小深度，即到葉子節(jié)點的最短步長，可通過層序遍歷的非遞歸方式，當(dāng)結(jié)點沒有兒子節(jié)點時，終止遍歷，返回當(dāng)前的層數(shù)，即最小的深度。

3.C++代碼

//我的代碼：（beats 91%） int minDepth(TreeNode*p) {if (p == NULL)return 0;int deepth = 0;bool flag = 1;queue<TreeNode*>q;q.push(p);while (!q.empty()&&flag){deepth++;int n = q.size();for (int i = 0; i < n; i++){TreeNode*tmp = q.front();q.pop();if (tmp->left)q.push(tmp->left);if (tmp->right)q.push(tmp->right);if (tmp->left == NULL&&tmp->right == NULL){flag = 0;break;}}}return deepth; } //遞歸方法 int minDepth(TreeNode*p) {if (p == NULL)return 0;if (p->left == NULL || p->right == NULL)return 1;else{int l = minDepth(p->left);int r = minDepth(p->right);if (l == 0)l = r;if (r == 0)r = l;return min(l, r) + 1;} }

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