以下代码找不到最后一个数100001,错在哪里?帮找下原因.
/*100000个数从小到大排列，输入任意数找出其所在位置，无则输出“无此数”，用折半查找法*/
#include <stdio.h>
main()
{
    int a[100000];
    int i,b,sta,mid,end;
    for(i=0;i<100000;i++)
    {    
        a[i]=i+1;
    }
    a[99999]=100001;
    printf("%d\n",a[99999]);
line1:
    sta=1,mid=100000/2,end=100000;
    printf("b=\n");
    scanf("%d",&b);
    for(i=1;i<=100000;i++)
    {
       if(b<a[mid-1])
       {
          end=mid;
          mid=sta+(end-sta)/2;
       }
       else if(b>a[mid-1])
       {
          sta=mid;
          mid=sta+(end-sta)/2 ;
       }
       else
       {
           printf("在第%d位\n",mid);
           mid=-1;
           break;
       }         
    }
    if(mid!=-1) printf("查无此数\n");
    if(getch()!=13) goto line1;
}

你定义的组数有点太大了吧，
我试着定义10，也找不到最后一个数，
end=11,赋这值就可以找到了。多加1

c语言数组的下标应该从0开始
sta=0,end=100000-1,mid=(sta+end)/2;

我昨晚找到了原因,我的算法必须将数列个数视为N+1个,即初始end=n+1,这样就能保证查找最后一位数.

#include <stdio.h>
#define SIZE 10
main()
{
    int a[SIZE];
    int i,b,sta,mid,end;
    for(i=0;i<SIZE-2;i++)
    {     
        a[i]=i+1;
        printf("%d  ",a[i]);
    }
    a[9]=11;
    printf("%d  ",a[SIZE-1]);
 
line1:
    sta=0,mid=SIZE/2,end=9;
    printf("b=");
    scanf("%d",&b);
    for(i=0;i<SIZE;i++)
    {
       if(b==a[mid] && mid<SIZE)
       {
           printf("number is %d\n",mid);
           mid=-1;
           break;
       }         
       else if(b<a[mid] && mid<SIZE)
       {
          end=mid-1;
          mid=(end-sta)/2;
       }
       else if(b>a[mid] && mid<SIZE)
       {
          sta=mid+1;
          mid=sta+(end-sta)/2 ;
       }
 
    }
    if(mid!=-1) printf("NO this count\n");
    printf("are you again y or n    ");
    if(getch()=='y') goto line1;
}

一个折半法的例子供你参考，学习其它的可以访问这，http://www.
例子在linux gcc下编译和运行
#include <stdio.h>

#define SIZE 10

void print_array(int array[SIZE]) {
        int i = 0;

        printf("The data in array:\n");
        for (i = 0; i < SIZE; ++i)
                printf("%4d", array[i]);
}

int find(const int array[SIZE],
                 const int low,
                 const int high,
                 const int target) {
        int pos = 0;

        if (low > high)
                return -1;

        pos = (low + high) / 2;

        if (target > array[pos]){
                return find(array, pos + 1, high, target);
        }
        else if (target < array[pos]) {
                return find(array, low, pos - 1, target);
        }
        else {
                return pos;
        }
}

int main() {
        int array[SIZE] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        int p = 0;
        int target = 0;

        print_array(array);

        printf("\nPlease input a data:");
        scanf("%d", &target);

        p = find(array, 0, SIZE-1, target);

        if (-1 == p)
                printf("Can't find %d in this array.\n", target);
        else
                printf("%d is the %dth(st/nd) element.\n",
                        target, p + 1);

        return 0;
}
"c101.c" [New] 54L, 893C written
[root@localhost ccc]# gcc c101.c
[root@localhost ccc]# ./a.out
The data in array:
   1   2   3   4   5   6   7   8   9  10
Please input a data:6
6 is the 6th(st/nd) element.

#include <stdio.h>
main()
{
  int a[1000],i,f,min,max,c=0;
  min=0;
  max=1000;
  for (i=0;i<1000;i++)
    a[i]=i+1;
  scanf("%d",&f);
  while((max-min)!=1)
  {
     i=(min+max)/2;
     if (f>a[i])
       min=i;
     else if (f<a[i])
       max=i;
     else
     {
       printf("%d is found in a[%d]",f,i);
       c=1;
       break;
     }

   }
   if (!c)
     printf("%d is not found",f);
   getch();

}

我的好像可以额

#include <stdio.h>
#include<conio.h>
main()
{
    int a[100000];
    int i,b,sta,mid,end;
    for(i=0;i<100000;i++)
    {   
        a[i]=i;
    }
    a[99999]=100001;
    printf("%d\n",a[99999]);
line1:
 //   sta=1,mid=100000/2,end=100000;
    sta=0,mid=99999/2,end=99999;
    printf("b=\n");
    scanf("%d",&b);
//    b=getchar();
  //  for(i=1;i<=100000;i++)
    do
    {
       if(b<a[mid])
       {
          end=mid-1;
          mid=sta+(end-sta)/2;
       }
       else
           if(b>a[mid])
           {
                sta=mid+1;
                mid=sta+(end-sta)/2 ;
            }
            else
                if(b==a[mid])
                {
                     printf("在第%d位\n",mid);
                     mid=-1;
                    break;
                }  
      if(sta>end)
          break;
    }while(mid!=-1);


    if(mid!=-1) printf("查无此数\n");

     goto line1;

    return 0;
}

[ 本帖最后由 mfh 于 2009-8-24 14:40 编辑 ]