c - 二分查找找不到正确的值

Question

我创建了一个包含 1000 个元素的 vector ，元素的值就是索引本身 V[100] = 100，V[50] = 50 等等

当我按值调用二分搜索时，它必须返回索引，它本身是什么 所以binary_search(vector, begin, end, 50)必须返回给我50，但返回30。我尝试用gdb调试，但找不到任何错误。

代码:

int rbb(int *v, int left, int right, int val) 
{

    int mid = (left + right) / 2;  //middle element

    if (right < left) //stop codition, pointers shifted
        return -1;

    if (val == v[mid]) //found value
        return mid;  

    if (val > v[mid]) //value is on vector right portion
        rbb(v, mid+1, right, val);

    if (val < v[mid]) //value is on vector left portion
        rbb(v, left, mid-1, val);

}

int main () 
{

    int v[1000];

    for (int i = 0; i < 1000; i++)
        v[i] = i;

    int x = rbb(v, 0, 999, 300);
    printf("%d", x);
}

Answer 1

您的代码的问题是您没有从递归调用 if rbb 函数返回值。您应该修改您的代码

if (val > v[mid]) //value is on vector right portion
    return rbb(v, mid+1, right, val);

if (val < v[mid]) //value is on vector left portion
    return rbb(v, left, mid-1, val);