writer：pprp

date: 20171103

题目描述

给定一棵二叉树的中序和层序输出，判断是否为平衡二叉树的。如果是，输出YES如果不是输出NO。

输入

树结点个数

中序遍历序列

层序遍历序列

输出

是否是平衡二叉树的判断结论

样例输入

样例1：

3

1 2 3

2 1 3

样例2：

4

1 2 3 4

1 2 3 4

样例输出

样例1：

YES

样例2：

NO

代码如下：

//M: 判别平衡二叉树
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>

using namespace std;
const int maxn = 1000;
int n;

struct tree
{
    tree * lchild;
    tree * rchild;
    int val;
    tree():lchild(NULL),rchild(NULL),val(0) {}
};

tree* createTree(int * layer, int * in,int n)
{
    if(n == 0)
        return NULL;
    int rin[maxn],lin[maxn],rlayer[maxn],llayer[maxn];
    memset(rin,0,sizeof(rin)),memset(lin,0,sizeof(lin));
    memset(rlayer,0,sizeof(rlayer)),memset(llayer,0,sizeof(llayer));
    tree * node = new tree;
    node->val = layer[0];
    int index = 0;
    for(index = 0 ; index < n ; index++)
        if(in[index] == layer[0])
            break;
    if(index == n)
    {
        cout << "Not found 404" << endl;
        return NULL;
    }
    int cnt = 0;
    for(int i = 0; i < index; i++)
        lin[cnt++] = in[i];
    cnt = 0;
    for(int i = index+1 ; i < n; i++)
        rin[cnt++] = in[i];

    int llayercnt = 0, rlayercnt = 0;
    for(int i = 1 ; i < n; i++)
    {
        for(int j = 0 ; j < index; j++)
        {
            if(lin[j] == layer[i])
                llayer[llayercnt++] = layer[i];
        }
    }
    for(int i = 1; i < n ; i++)
    {
        for(int j = 0 ; j < cnt; j++)
        {
            if(rin[j] == layer[i])
                rlayer[rlayercnt++] = layer[i];
        }
    }
    node->lchild = createTree(llayer,lin,llayercnt);
    node->rchild = createTree(rlayer,rin,rlayercnt);
    return node;
}

bool solve(tree * root, int& depth)
{
    if(root == NULL)
    {
        depth = 0;
        return true;
    }
    int leftdepth, rightdepth;
    bool bleft = solve(root->lchild,leftdepth);
    bool bright = solve(root->rchild,rightdepth);

    if(bleft && bright)
    {
        if(abs(leftdepth-rightdepth)<=1)
        {
            depth = 1+(leftdepth>rightdepth?leftdepth:rightdepth);
            return true;
        }
    }
    return false;
}

void post(tree * root)
{
    if(root != NULL)
    {
        post(root->lchild);
        post(root->rchild);
        cout << root->val << " ";
    }
}

int main()
{
    int n;
    cin >> n;
    int layer[maxn],in[maxn];
    for(int i = 0 ; i < n; i++)
        cin >> in[i];
    for(int j = 0 ; j < n ;  j++)
        cin >> layer[j];
    tree * root = createTree(layer,in,n);
    int depth = 0;
//    post(root);
//    cout << endl;

    if(solve(root,depth))
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    return 0;
}