程序员面试题精选100题(60)-判断二叉树是不是平衡

// 程序员面试题精选100题(60)-判断二叉树是不是平衡.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
using namespace std;

struct TNode{
char chValue;
TNode *leftChild;
TNode *rightChild;
};
TNode* rebuildTree(char *preOrder,int start1,char *midOrder,int start2,int n)//根据前序和中序建立二叉树 长度为N
{
TNode *root;
if(n==0) return NULL;
root = new TNode;
int pivet;
char chroot;
chroot=preOrder[start1];
root->chValue = chroot;
for(int i=start2;i<start2+n;i++)//include start1
{
if(midOrder[i]==chroot) { pivet = i;break;}
}
if(pivet-start2>0)
root->leftChild=rebuildTree(preOrder,start1+1,midOrder,start2,pivet-start2);
else root->leftChild = NULL;
if(n-pivet+start2-1>0)//pivet-start2 is the half number,
root->rightChild=rebuildTree(preOrder,start1+1+pivet-start2,midOrder,pivet+1,n-pivet+start2-1);
else root->rightChild = NULL;
return root;
}
void preprint(TNode *root)
{
if(root!=NULL)
{
cout<<root->chValue<<" ";
preprint(root->leftChild);
preprint(root->rightChild);
}
}
int flag=1;
int isbalance(TNode *root)
{
if (flag==0)
{
return -1;
}
if (root==NULL)
{
return 0;
}
int h1=isbalance(root->leftChild)+1;
int h2=isbalance(root->rightChild)+1;
if (abs(h1-h2)>1)
{
flag=0;
}
return h1>h2?h1:h2;
}
//////////////////////////////////////////////////////////////////////////
bool IsBalanced(TNode* pRoot, int* pDepth)
{
if(pRoot == NULL)
{
*pDepth = 0;
return true;
}

int left, right;
if(IsBalanced(pRoot->leftChild, &left)
&& IsBalanced(pRoot->rightChild, &right))
{
int diff = left - right;
if(diff <= 1 && diff >= -1)
{
*pDepth = 1 + (left > right ? left : right);
return true;
}
}

return false;
}
bool IsBalanced(TNode* pRoot)
{
int depth = 0;
return IsBalanced(pRoot, &depth);
}

int _tmain(int argc, _TCHAR* argv[])
{
TNode* rootparent,*rootchild;
int n,m;
cout<<"input n"<<endl;
cin>>n;
char *preOrder=new char
;
char *midOrder=new char
;
cout<<"input preorder1"<<endl;
for(int i=0;i<n;i++)
cin>>preOrder[i];
cout<<"input midorder1"<<endl;
for(int i=0;i<n;i++)
cin>>midOrder[i];
rootparent=rebuildTree(preOrder,0,midOrder,0,n);
preprint(rootparent);
cout<<endl;
isbalance(rootparent);
if (flag==1)
{
cout<<"is balance "<<endl;
}
else
{
cout<<"is not balance "<<endl;
}
cout<<IsBalanced(rootparent);
system("pause");
return 0;
}