向量<int,int>的比较器. [英] Comparator for vector<pair<int,int>>
问题描述
vector<pair<int,int> > v;
for(i=0;i<5;i++){
cin>>b>>c;
v.push_back(make_pair(b,c));
}
sort(v.begin(),v.end());
是否有可能为排序函数编写一个比较器,以便对 v [i] .first
进行递增排序,并对类似值的 v [i] .first 进行排序code>,
v [i] .second
以降序排序?
像:-
i/p:
Is it possible to write a comparator for the sort function such that v[i].first
is sorted in increasing order and for similar values of v[i].first
, v[i].second
is sorted in decreasing order?
like:-
i/p:
13 10
44 15
13 15
13 99
6 45
o/p:
6 45
13 99
13 15
13 10
44 15
推荐答案
当然,这很容易.
您需要做的就是编写一个具有以下签名的函数:
All you need to do is write a function with this signature:
bool f(std::pair<int, int> lhs, std::pair<int, int> rhs);
当且仅当 lhs<rhs
因此,根据您的标准,如果满足以下条件,则 lhs
小于 rhs
:
So, by your criteria, lhs
is smaller than rhs
if:
-
lhs.first<rhs.first
, - 或
lhs.first == rhs.first&&lhs.second>rhs.second
因此,基本上将它们放在一起,就可以得到:
So, basically just put those together, and you get:
bool mycomparer(std::pair<int, int> lhs, std::pair<int, int> rhs) {
if (lhs.first < rhs.first) {
return true;
}
else if (lhs.first == rhs.first && lhs.second > rhs.second) {
return true;
}
else {
return false;
}
}
这可以写得更紧凑,但是我想保持它的简单和可读性以阐明要点.:)
This could be written much more compactly, but I wanted to keep it simple and readable to get the point across. :)
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