有15个数按由大到小顺序存放在一个数组中，输入一个数，要求用折半查找法找出该数是数组中第几个元素的值．

[lc113117996]

#include<stdio.h>
void main()
{
int a[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1};
int i,left=0,right=14,flag=0,d,mid;
printf("shuru:");
scanf("%d",&d);
if(d>a[14]||d<a[0])
{ printf("\nchongxin:");
scanf("%d",&d);}
for(i=1;i<3;i++)
{ mid=(left+right)/2;
if(d==a[mid])
{ printf("di %d ge.\n",mid);
flag=1;break;}
else if(d>a[mid])
right=mid-1;
else left=mid+1; }
if(flag==0) printf("wushu.\n");
}

请看看哪个地方错了，谢谢了

[liliangbao]

#include <stdio.h> 
void main() 
{ 
  int a[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; 
  int i,left=0,right=14,flag=0,d,mid; 
printf("shuru:"); 
scanf("%d",&d); 
if(d < a[14]||d >a[0]) 
  { printf("\nchon gxin:"); 
  scanf("%d",&d);} 
  for(i=1;i <5;i++) //16个最多比较4次 
{
    mid=(left+right)/2; 
    if(d==a[mid]) 
{  
    printf("di %d ge.\n",mid); 
    flag=1;break;
} 
else if(d>a[mid]) 
  right=mid-1; 
else left=mid+1;
} 
if(flag==0)  printf("wushu.\n"); 
} 

[qq675927952]

#include <stdio.h> 
int main() 
{ 
  int a[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; 
  int i,left=0,right=14,flag=0,d,mid; 
   printf("shuru:"); 
    scanf("%d",&d); 
   if(d<a[14]||d >a[0]) //这你写错了
  { 
    printf("\nchongxin:"); 
    scanf("%d",&d);
  } 
 // for(i=1;i <3;i++) //这有问题，
 while(true) 
  {  
      mid=(left+right)/2; 
     if(d==a[mid]) 
    { 
      printf("di %d ge.\n",mid); 
       flag=1;
       break;
    } 
    else if(d>a[mid]) 
     right=mid-1; 
    else left=mid+1; 
 } 
  if(flag==0)  
   printf("wushu.\n"); 
   getchar();  //让程序暂停一下
   getchar(); 
   getchar(); 
}

[xiaocha]

修正了3楼的错误, 并改为查找函数和与数组大小无关的代码,
如要改变数据, 仅需修改数组 data 一行
没有测试, 如有错误, 欢迎指正

#include <stdio.h> 

// find 函数调用, data 必须从大到小排列
int find(int *data, int count, int value)
{
  int left = 0, right = count-1, mid; 
  
  while(1)
  {  
    if(left > right) return -1;

    mid = (left + right) / 2; 

    if (value == data[mid]) 
      return mid;
    else if (value > data[mid])
      right = mid - 1; 
    else
      left = mid + 1; 
  } 
}

int main() 
{ 
  int data[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; // 如要改变数据, 仅需修改此行
  int value, index;
  int count = sizeof(a) / sizeof(a[0]);

  printf("输入要找的数:"); 
  scanf("%d",&value); 
  while (value>a[count-1]||value<a[0])
  { 
    printf("\n重新输入要找的数:"); 
    scanf("%d",&value); 
  } 
  
  index = find(data, count, value);

  if (index < 0)
    printf("\n没找到 %d.\n", value); 
  else
    printf("\n在第 %d 个.\n", index);

  getchar(); 
} 

[ouzhf]

#include <stdio.h> 
void main() 
{ 
	int a[15] = {15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; 
	int left, right, flag, d, mid; 

	printf("shuru:"); 
	scanf("%d", &d); 

	if(d < a[14] || d > a[0])  //不在数组范围内
	{ 
		printf("\nchongxin:"); 
		scanf("%d",&d);
	} 

	left = 0;
	right = 14;
	flag = 0;

	while (left <= right)
	{  
		mid = (left + right) / 2; 
		if (d == a[mid]) 
		{  
			printf("di %d ge.\n",mid); 
			flag = 1;
			break;
		} 
		else 
			if (d > a[mid]) 
				right = mid - 1; 
			else 
				left = mid + 1;  
	}

	if (flag == 0)  
		printf("wushu.\n"); 
}

[blems]

#include <stdio.h> 
int main() 
{ 
  int a[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1}; 
  int i,left=0,right=14,flag=0,d,mid; 
  printf("shuru:"); 
  scanf("%d",&d); 
if(d<a[14]||d >a[0]) //<-----------------楼主这个地方写错了
{
	 printf("\nchongxin:"); 
  	 scanf("%d",&d);
} 
for(;left!=right;)   //<----------------判断条件
{  mid=(left+right)/2; 
   if(d==a[mid])
   { 
        printf("di %d ge.\n",mid); 
	flag=1;break;
   } 
   else if(d>a[mid])
           right=mid-1; 
   else
        left=mid+1; 
} 
if(d==a[left])   //<---------------这个地方再加一个判断
{  
   printf("di %d ge.\n",mid);
   flag=1;
} 
if(!flag)
   printf("wushu.\n"); 
   return 0；
}

[gtl022]

#include <stdio.h>
int main()
{
int a[15]={15,14,13,12,11,10,9,8,7,6,5,4,3,2,1};
int i,left=0,right=14,flag=0,d,mid;
printf("shuru:");
scanf("%d",&d);
if(d<a[14]||d >a[0]) //这你写错了
{
printf("\nchongxin:");
scanf("%d",&d);
}
// for(i=1;i <3;i++) //这有问题，
while(true)
{
if(left == right) //add below two line
break;
mid=(left+right)/2;
if(d==a[mid])
{
printf("di %d ge.\n",mid);
flag=1;
break;
}
else if(d>a[mid])
right=mid-1;
else left=mid+1;
}
if(flag==0)
printf("wushu.\n");
getchar(); //让程序暂停一下
getchar();
getchar();
}