简单二分查找模板（查找）

# include <stdio.h>

int search(int a[], int n, int v)    //这个好像是效率最高的
{
    int left = -1, right = n, middle;
    while(left+1 != right)
    {
        middle = left + (right-left) / 2;
        if(a[middle] < v)
            left = middle;
        else
            right = middle;
    }
    if(right >= n || a[right] != v)
        right = -1;
    return right;
}

int search1(int a[], int n, int v)
{
    int left = 0, right = n-1, middle;
    while(left <= right)
    {
        middle = (left+right) / 2;
        if(a[middle] > v)
        right = middle - 1;
        else if(a[middle] < v)
        left = middle +1;
        else
        return middle;
    }
    return -1;
}

int search2(int a[], int n, int v)
{
    int left = 0, right = n, middle;
    while(left < right)
    {
        middle = (right + left) / 2;
        if(a[middle] > v)
        right = middle;
        else if(a[middle] < v)
        left = middle + 1;
        else
        return middle;
    }
    return -1;
}

int a[1000000];
int main(void)
{
    int n, i, t, ans;
    while(~scanf("%d", &n))
    {
        for(i = 0; i < n; i++)
            scanf("%d", &a[i]);
        scanf("%d", &t);
        ans = search(a, n, t);
        if(ans <= 0)
            printf("NO
");
        else
            printf("YES
");
    }

    return 0;
}