迭代对的向量 [英] Iterate over vector of pair

问题描述

我已经编写了以下代码片段，但它似乎不起作用.

I have written following code snippet but it does not seem to be working.

int main(){
    int VCount, v1, v2;
    pair<float, pair<int,int> > edge;
    vector< pair<float, pair<int,int> > > edges;
    float w;
    cin >> VCount;
    while( cin >> v1 ){
        cin >> v2 >> w;
        edge.first = w;
        edge.second.first = v1;
        edge.second.second = v2;
        edges.push_back(edge);
    }
    sort(edges.begin(), edges.end());
    for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ; itt != edges.end; it++){
        cout >> it.first;
    }
    return 0;
}

它在包含 for 循环的行上抛出错误.错误是:

It is throwing an error at the line containing for loop. The error is:

error: no match for ‘operator<’ in ‘it < edges.std::vector<_Tp, _Alloc>::end [with _Tp = std::pair<float, std::pair<int, int> >, _Alloc = std::allocator<std::pair<float, std::pair<int, int> > >, std::vector<_Tp, _Alloc>::const_iterator = __gnu_cxx::__normal_iterator<const std::pair<float, std::pair<int, int> >*, std::vector<std::pair<float, std::pair<int, int> > > >, typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::const_pointer = const std::pair<float, std::pair<int, int> >*]

有人可以帮我吗?

推荐答案

循环中至少有三个错误.

There are at least three errors in the loop.

for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ; itt != edges.end; it++){
        cout >> it.first;
    }

首先你必须使用 edges.end() 而不是 edges.end.而身体内部必须有

First of all you have to use edges.end() instead of edges.end. And inside the body there has to be

    cout << it->first;

代替

    cout >> it.first;

为了避免此类错误，您可以简单地编写

To escape such errors you could write simply

for ( const pair<float, pair<int,int> > &edge : edges )
{
   std::cout << edge.first;
}

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