关于STL的排序，和比较参数cmp

stable_sort

template <class RandomAccessIterator> void stable_sort ( RandomAccessIterator first, RandomAccessIterator last );

  void stable_sort ( RandomAccessIterator first, RandomAccessIterator last,
                     Compare comp );

Sort elements preserving order of equivalents

Sorts the elements in the range  [first,last) into ascending order, like  sort, but  stable_sort grants that the relative order of the elements with equivalent values is preserved.

The elements are compared using  operator< for the first version, and  comp for the second.

Parameters

first, last

  [first,last)

comp

Comparison function object that, taking two values of the same type than those contained in the range, returns  true  if the first argument goes before the second argument in the specific strict weak ordering（严格偏序） it defines, and false otherwise.

bool cmp(Record a,Record b);

默认是增序，即若a.key < b.key， return true,按增序排列。

若a.key > b.key return true,则实际是按减序排列的

也可以定义相等时的大小比较来定义第二阶的排序

// stable_sort example #include <iostream> #include <algorithm> #include <vector> using namespace std; bool compare_as_ints (double i,double j) { return (int(i)<int(j)); } int main () { double mydoubles[] = {3.14, 1.41, 2.72, 4.67, 1.73, 1.32, 1.62, 2.58}; vector<double> myvector; vector<double>::iterator it; myvector.assign(mydoubles,mydoubles+8); cout << "using default comparison:"; stable_sort (myvector.begin(), myvector.end()); for (it=myvector.begin(); it!=myvector.end(); ++it) cout << " " << *it; myvector.assign(mydoubles,mydoubles+8); cout << "/nusing 'compare_as_ints' :"; stable_sort (myvector.begin(), myvector.end(), compare_as_ints); for (it=myvector.begin(); it!=myvector.end(); ++it) cout << " " << *it; cout << endl; return 0; } 

1046. Plane Spotting

#include<iostream> #include<vector> #include<algorithm> using namespace std; struct info{ int noq;int start;int end;double average;}; bool cmpA(info a,info b) { if(a.average<b.average) return true; else return false; } bool cmpQ(info a,info b) { if(a.noq<b.noq) return true; else return false; } bool cmpE(info a,info b) { if(a.end > b.end) return true; else return false; } bool cmp(info a,info b) { if(a.average > b.average) return true; else if(a.average < b.average) return false; else { if(a.noq>b.noq) return true; else if(a.noq < b.noq) return false; else return (a.end<b.end) ; } } int main() { int N; cin>>N; for(int ni = 0;ni<N;ni++) { int q;//number of quarters int p;//number of periods int m;//min number of quarters cin>>q>>p>>m; int *arr = new int [q+1]; for(int i = 1;i<=q;i++) cin>>arr[i]; if(q<=m) { cout<<"Result for run "<<ni+1<<":"<<endl; cout<<1<<"-"<<q<<endl; continue; } vector<info> v; info tmp; for(int j = m;j<=q;j++) for(int i = 1;i<=q-j+1;i++) { tmp.noq = j; tmp.start = i; tmp.end=i+j-1; tmp.average = 0; for(int l = 0;l<j;l++) tmp.average+=arr[i+l]; tmp.average /= (j*0.1); v.push_back(tmp); } // stable_sort(v.begin(),v.end(),cmpE); //stable_sort(v.begin(),v.end(),cmpQ); //stable_sort(v.begin(),v.end(),cmpA); sort(v.begin(),v.end(),cmp); cout<<"Result for run "<<ni+1<<":"<<endl; for(int i = 0;i<p;i++) cout<<v[i].start<<"-"<<v[i].end<<endl; delete arr; } return 0; }