C++ sort中cmp函数的正确使用-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_25310869/article/details/69666032

这篇博客探讨了C++中sort函数使用的自定义比较函数cmp的常见错误，指出当两个数相等时返回invalid <的问题。博主强调了正确的做法是在相等情况下返回false，确保排序的稳定性。

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bool myComp(const vector<int>& a, const vector<int>& b)
{

    /*if (a.at(1) != b.at(1))
        return a.at(1) < b.at(1);
    else if (a.at(2) != b.at(2))
        return a.at(2) < b.at(2);
    return false;*/
    if (a.at(1) == b.at(1))
        return true;
    return a.at(1) > b.at(1);


    //return a.at(1) > b.at(1);
}

void process(vector<vector<int>>& vecProcess) 
{
    vector<int> t1;
    t1.push_back(1);
    t1.push_back(9);
    t1.push_back(2);
    t1.push_back(5);

    vector<int> t2;
    t2.push_back(3);
    t2.push_back(6);
    t2.push_back(9);
    t2.push_back(2);

    vector<int> t3;
    t3.push_back(2);
    t3.push_back(4);
    t3.push_back(6);
    t3.push_back(8);

    vector<int> t4;
    t4.push_back(5);
    t4.push_back(6);
    t4.push_back(9);
    t4.push_back(6);

    vecProcess.push_back(t1);
    vecProcess.push_back(t2);
    vecProcess.push_back(t3);
    vecProcess.push_back(t4);


    sort(vecProcess.begin(), vecProcess.end(), myComp);
}

int main()
{
    vector<vector<int>> vecProcess;
    process(vecProcess);
    system("pause");
    return 0;
}