这个前K&R ch3错了吗？

Question

像这样的代码,在第44页.

int binsearch(int x, int v[], int n)
{
    int low, high, mid;

    low = 0;
    high = n - 1;
    while(low <= high){
        mid = (high+low)/2;
        if(x < v[mid]){
            high = mid + 1;
        }else if(x > v[mid]){
            low = mid + 1;
        }else{
            return mid;
        }
        printf("mid is %d\n",mid);
    }

    return -1;
}

int main(void)
{
    int v[] = {2,3,4,7,8,23,54,65,76};
    int ret = binsearch(7, v, sizeof(v)/sizeof(int));

    printf("%d,ret is %d\n", sizeof(v),ret);
    return 0;
}

编译并运行它,结果是死循环!所以行"low = mid + 1;" 应该采取"低=中;",是吗？thx.

Answer 1

您发布的代码中的问题不是值low,但在测试值的设置中high...如果x小于v[mid],则新索引值high应小于,不大于mid.所以你想改变以下内容:

if(x < v[mid]){
    high = mid + 1;

至:

if(x < v[mid]){
    high = mid - 1;

你可以在这里看到一个有效的例子:http://ideone.com/E6Ma8