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二分查找:

 

完整代码：

#include<stdio.h>
#include<stdlib.h>
int main()
{
    int array[6]={1,2,5,6,7,8};
    int arrayLengh=6;
    int low=0;
    int high=arrayLengh-1;
    int index=-1;
    int mid;
    int target;
    printf("input you look for:\n");
    scanf("%d",&target);
    while(low<=high)
    {
        mid=(low+high)/2;
    if(array[mid]==target)
        {
        index=mid;
        break;
        }
    else if(array[mid]<target)
        {
        low=mid+1;
        }
    else
        {
        high=mid-1;
        }
    }
    if(index==-1)
        printf("NOT FOUND!\n");
    else
        printf("FOUND IT! the index=%d\n",index);
return 0;
}