【内功】基础算法——二分查找

1. 自己实现 lower_bound, upper_bound

int my_lower_bound(vector<int> nums, int target) {
    int left = 0, right = nums.size();
    while (left < right) {
        long long mid = left + (right - left) / 2;
        if ((nums[mid] < target) {
            left = mid + 1;
        } else {
            right = mid;
        }
    }
    return left;
}

int my_upper_bound(vector<int> nums, int target) {
    int left = 0, right = nums.size();
    while (left < right) {
        long long mid = left + (right - left) / 2;
        if ((nums[mid] > target) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
    return left;
}