面试题39：获得二叉树深度和判断是否是平衡二叉树

1， 二叉树深度，一个简单的递归

2， 是否是平衡二叉树，一个略复杂的递归

见代码：

#include<iostream>

using namespace std;

struct TreeNode{
TreeNode* pleft;
TreeNode* pright;
int value;

TreeNode(int v){
value = v;
pleft = NULL;
pright = NULL;
}
};

TreeNode* build_tree(){
TreeNode* T1 = new TreeNode(1);
TreeNode* T2 = new TreeNode(2);
TreeNode* T3 = new TreeNode(3);
TreeNode* T4 = new TreeNode(4);
TreeNode* T5 = new TreeNode(5);
TreeNode* T6 = new TreeNode(6);
TreeNode* T7 = new TreeNode(7);
TreeNode* T8 = new TreeNode(8);
TreeNode* T9 = new TreeNode(9);
TreeNode* T10 = new TreeNode(10);
TreeNode* T11 = new TreeNode(11);
T1->pleft = T2;
T1->pright = T3;
T2->pleft = T4;
T2->pright = T5;
T3->pleft = T6;
T3->pright = T7;
T6->pleft = T8;
T6->pright = T9;
T9->pleft = T10;
T9->pright = T11;
return T1;
}

int get_deeps(TreeNode* root){
if(root == NULL){
return 0;
}
int left_deeps = get_deeps(root->pleft);
int right_deeps = get_deeps(root->pright);
return left_deeps > right_deeps? (left_deeps+1):(right_deeps+1);

}

bool is_balance(TreeNode* root){
if(root == NULL){
return true;
}
int left_deeps = get_deeps(root->pleft);
int right_deeps = get_deeps(root->pright);
int diff = left_deeps - right_deeps;
if(diff > 1 || diff < -1){
return false;
}
return is_balance(root->pleft) && is_balance(root->pright);
}
int main(){
// 1
// / \
// 2 3
// / \ / \
// 4 5 6 7
// / \
// 8 9
// / \
// 10 11
TreeNode* root = build_tree();
int deeps = get_deeps(root);
cout << "deeps: "<< deeps << endl;
bool is_balanced = is_balance(root);
cout << "balance:" << is_balanced << endl;
return 0;
}