C++ 迭代对的向量
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Iterate over vector of pair
提问by Peeyush
I have written following code snippet but it does not seem to be working.
我已经编写了以下代码片段，但它似乎不起作用。
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;
}
It is throwing an error at the line containing for loop. The error is:
它在包含 for 循环的行上抛出错误。错误是：
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> >*]
Can anyone help me out?
谁能帮我吗？
回答by Vlad from Moscow
There are at least three errors in the loop.
循环中至少有三个错误。
for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ; itt != edges.end; it++){
cout >> it.first;
}
First of all you have to use edges.end()instead of edges.end. And inside the body there has to be
首先，您必须使用edges.end()而不是edges.end. 在身体内部必须有
cout << it->first;
instead of
代替
cout >> it.first;
To escape such errors you could write simply
为了避免此类错误，您可以简单地编写
for ( const pair<float, pair<int,int> > &edge : edges )
{
std::cout << edge.first;
}
回答by P0W
for ( vector < pair<float,pair<int,int>> >::const_iterator it = edges.begin() ;
it != edges.end () ; // Use (), and assuming itt was a typo
it++)
{
cout << it->first; // Use ->
}
Also, you might want to add a custom comparator for std::sort
此外，您可能希望为 std::sort
