二分查找等于target、第一个小于等于target、第一个大于等于target的值

class Solution {
public:
    // 查找第一个小于等于target的值
    int binarySearch1(vector<int> vec, int target) {
        int left = 0;
        int right = vec.size() - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (vec[mid] > target) { // 目标值可能在区间[left, mid]
                right = mid - 1;
            } else { // 目标值可能在区间[mid, right]
                left = mid + 1;
            }
        }
        return right;
    }
    // 查找第一个大于等于target的值
    int binarySearch2(vector<int> vec, int target) {
        int left = 0;
        int right = vec.size() - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (vec[mid] < target) { // 目标值可能在区间[mid, right]
                left = mid + 1;
            } else { // 目标值可能在区间[left mid]
                right = mid - 1;
            }
        }
        return right;
    }
    // 查找等于target的值
    int binarySearch3(vector<int> vec, int target) {
        int left = 0;
        int right = vec.size() - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (vec[mid] == target) {
                return mid;
            } else if (vec[mid] > target) { // 目标值可能在区间[left, mid]
                right = mid - 1;
            } else { // 目标值可能在区间[mid, right]
                left = mid + 1;
            }
        }
        return -1;
    }
};