Question

我尝试使用带有键的std :: map作为Struct，但是找不到键就失败了。这有什么不对？查找未找到，但插入不会更改地图中的计数.....

#pragma once
#include <map>
struct OccTestdef
{

public:
    int Typ;
    int Length;

    OccTestdef(int typ,  int length) :Typ(typ), Length(length) {};

    bool operator < (const OccTestdef& R) const
    {
        if (Typ < R.Typ)  return true;
        if (Length < R.Length) return true;
        return false;
    }

};


typedef std::map<OccTestdef, int> Testmap;
typedef std::pair<OccTestdef, int> Testpair;

class testocc
{
public:
    testocc();
    ~testocc(){}

    bool runtest();

private:
    Testmap tests;

    int addOrInsert(int left, int num, int value);

};

和cpp：

#include "testocc.h"

testocc::testocc()
{
    tests = Testmap();
}

// Will Return the Map-Value if found or -1 if new Inserted
int testocc::addOrInsert(int left, int num, int value)
{
    int res;
    OccTestdef tn(left, num);
    auto result = tests.find(tn);
    if (result != tests.end()) {
        res = result->second;
    }
    else
    {
        tests.insert(Testpair(tn, value));
        res = -1;
    }
    return res;
}

bool testocc::runtest()
{
    int res;
    bool result;
// Fill map with 4 Entries
    tests.insert(Testpair( OccTestdef(1, 100), 1));
    tests.insert(Testpair(OccTestdef(1, 200), 2));
    tests.insert(Testpair(OccTestdef(1, 300), 3));
    tests.insert(Testpair(OccTestdef(1, 400), 4));


    result = (tests.size() == 4);
// Try to find or Insert 
     res = addOrInsert(1, 200, 2);
    //res should be 2 
    result = (res == 2);

    result = (tests.size() == 4);

    res = addOrInsert(2, 200, 20);
    // Res must be -1 because new inserted
    result = (res == -1);

    // Count is not changed
    result = (tests.size() == 5);


//These fails why?
    res = addOrInsert(2, 200, 20);
    //res should be 20 
    result = (res == 20);
    return result;
}

我不明白为什么test.find（）没有按预期工作。

Answer 1

您的opeator<不会正确排序您的元素，因为如果Typ较小或Length较小，则返回true。

#include <tuple>

bool operator < (const OccTestdef& R) const
{
    return std::tie(Typ, Length) < std::tie(R.Typ, R.Length);
}

std :: map with struct as key

1 个答案: