upper_bound和lower_bound

 vector<int>::iterator it;

    //vector<int> d = { 1,2,3,4,5,5,6,7,8,9 };//升序数组 
    //it = upper_bound(d.begin(), d.end(),5);  //第一个大于val
    // <=>it= upper_bound(d.begin(), d.end(), 5, less<int>());//默人用的less比较方式
    //it = lower_bound(d.begin(), d.end(), 5);  //第一个大于等于val
    // <=>it = lower_bound(d.begin(), d.end(), 5, less<int>());  
    //it = lower_bound(d.begin(), d.end(), 5, greater<int>());  //小过一半就找不到
    //it= upper_bound(d.begin(), d.end(), 5, greater<int>());//查找不到

    vector<int> d = { 9,8,7,6,5,5,4,3,2,1 }; //降序数组
     //it = upper_bound(d.begin(), d.end(),5);  //查找不到
     // it = lower_bound(d.begin(), d.end(), 5);  //大过一半就找不到
    //it = upper_bound(d.begin(), d.end(), 5, greater<int>());//第一个小于val
    it = lower_bound(d.begin(), d.end(), 5, greater<int>());//第一个小于等于val

    if (it != d.end()) { 
        cout << *it <<endl;
    }
    else {
        cout << "out of range"<<endl;
    }