代码随想录第十七天
平衡二叉树的判断
平衡二叉树是指二叉树中任意节点的子树的高度之差小于等于1,使用后序遍历先得到左右子树的高度,然后返回1+较大高度
代码如下:
class Solution {
public: int balanceTree(TreeNode* root) {
if (root == NULL) return 0; int leftHeight = balanceTree(root->left); if (leftHeight == -1) return -1; int rightHeight = balanceTree(root->right); if (rightHeight == -1) return -1; if (abs(leftHeight - rightHeight) > 1) return -1; else {
return (1 + max(leftHeight, rightHeight)); } } }
讯享网
打印二叉树的所有路径
讯享网class Solution {
public: vector<int> path; vector<string> result; void treeVersale(TreeNode* root, vector<int>& path, vector<string>& result) {
path.push_back(root->value); if (root->left==NULL&&root->right==NULL) {
int size = path.size(); string spath; for (size_t i = 0; i < size-1; i++) {
spath += to_string(path[i]); spath += "->"; } spath += to_string(path[size - 1]); result.push_back(spath); return; } if (root->left) {
treeVersale(root->left, path, result); path.pop_back(); } if (root->right) {
treeVersale(root->right, path, result); path.pop_back(); } return; } vector<string> binaryTreePaths(TreeNode* root) {
treeVersale(root, path, result); return result; } }
计算左叶子之和
class Solution {
public: int leftTree(TreeNode* root) {
if (root == NULL) return 0; int leftnum = leftTree(root->left); if (root->left!=NULL&&root->left->left==NULL&&root->left->right==NULL) {
leftnum = root->left->value; } int rightnum = leftTree(root->right); return leftnum + rightnum; } }

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