构建堆过程 [英] build heap procedure

问题描述

可能重复：

Possible Duplicate:
build heap procedure crash during it's worlking

 #include<iostream>
#include<math.h>
using namespace std;
#define  maxn 1000
int x[maxn];

int parent(int i){
    return int(i/2);

}
int left(int i){
    return 2*i;

}
int right(int i){
    return 2*i+1;

}
void  max_heap(int x[],int i,int size){
     bool s=true;
     int largest;
      for (int k=1;k<size/2;k++){
          if(x[k]< x[2*k] ||  x[k]<x[2*k+1]){
              s=false;
          }

      }
       if (s==true) return;
       else{

    if(i>=size) return ;

    int l=left(i);
    int r=right(i);

    if (l<=size &&  x[l]>x[i]){
        largest=l;
    }
    else
    {
        largest=i;
    }
    if (r<=size && x[r]>x[largest]){
    largest=r;
    }
    if (largest!=i)  { int s=x[i];x[i]=x[largest];x[largest]=s;}
       }
    max_heap(x,largest,size);
}
 void build(int x[],int size){
     int heapsize=size;
      for (int i=(size/2);i>1;i--)
          max_heap(x,i,size);


 }



int main(){

    x[1]=4;
    x[2]=1;
    x[3]=3;
    x[4]=2;
    x[5]=16;
    x[6]=9;
    x[7]=10;
    x[8]=14;
    x[9]=8;
    x[10]=7;
    build(x,10);
     for (int i=1;i<=10;i++)
         cout<<x[i]<<"  ";






    return 0;
}

此代码失败，而只有max_heap过程工作找到，请告诉我什么是错误的代码？我花了几个小时，但没有发现错误

this code fails,while only max_heap procedure works find,please tell me what is wrong in code?i have spent hours but did not find something wrong yet

推荐答案

我注意到的一件事是，为根元素调用 max_heap ：

One thing I noticed immediatly is that you don't call max_heap for the root element:

for (int i=(size/2);i>1;i--)
    max_heap(x,i,size);

应为

i>=1

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