#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> vec = {1, 2, 4, 4, 4, 6, 8, 10};
    int target = 4;

    // lower_bound
    auto lower = lower_bound(vec.begin(), vec.end(), target);
    cout << "lower_bound of " << target << " is at index: " << (lower - vec.begin()) << endl;

    // upper_bound
    auto upper = upper_bound(vec.begin(), vec.end(), target);
    cout << "upper_bound of " << target << " is at index: " << (upper - vec.begin()) << endl;

    // 找到最后一个小于 target 的元素
    if (lower != vec.begin()) {
        auto last_less = lower - 1;
        cout << "Last element less than " << target << " is " << *last_less << " at index " << (last_less - vec.begin()) << std::endl;
    } else
        cout << "No element is less than " << target << endl;

    // 找到最后一个小于等于 target 的元素
    if (upper != vec.begin()) {
        auto last_less_equal = upper - 1;
        cout << "Last element less than or equal to " << target << " is " << *last_less_equal
             << " at index " << (last_less_equal - vec.begin()) << endl;
    } else
        cout << "No element is less than or equal to " << target << endl;

    // 查找元素是否存在
    if (lower != vec.end() && *lower == target)
        cout << target << " exists in the array at index " << (lower - vec.begin()) << endl;
    else
        cout << target << " does not exist in the array." << endl;

    // 统计目标值出现个数
    int count = upper - lower;
    cout << "Count of " << target << " is: " << count << endl;
    return 0;
}