二分法解决问题模板

int binarySearch(int A[], int left, int right, int x) {
    int mid;
    while(left < right) {
        mid = (left + right) / 2;
        if(需要成立的条件)
            right = mid;
        else {
            left = mid + 1;
        }
    }
    return left;
}