hdu 1031 (partial sort problem, nth_element, stable_partition, lambda expression)

partial sort.
first use std::nth_element to find pivot,
then use std::stable_partition with the pivot to partition the largest k, whose indices are in acsending order, print them in reverse order.
p.s. lambda expression is also used.
STL is powerful.

#include <cstdio>#include <vector>#include <algorithm>struct IRPair{    int ind;    double rate;};int main() {    //freopen("input.txt","r",stdin);    int num_people, num_candidate, num_final, i,j;    double tmp;    std::vector<IRPair> vec;    std::vector<double> ratings;    while(scanf("%d%d%d",&num_people,&num_candidate,&num_final)!=EOF) {        vec.resize(num_candidate);        ratings.clear(); ratings.resize(num_candidate);        for(i=0;i<num_people;++i)        for(j=0;j<num_candidate;++j) { scanf("%lf",&tmp); ratings[j]+=tmp; }        for(i=0;i<num_candidate;++i) { vec[i].ind=i+1; vec[i].rate=ratings[i]; }        std::nth_element(&ratings[0],&ratings[num_candidate-num_final],&ratings[num_candidate]);        tmp=ratings[num_candidate-num_final];        std::stable_partition(&vec[0],&vec[num_candidate],[tmp](const IRPair &x) { return x.rate>=tmp; });        for(i=num_final-1;i>0;--i) { printf("%d ",vec[i].ind);}        printf("%d\n",vec[0].ind);    }    return 0;}

156 ms for double, vector
140 ms for float, vector
140 ms for double, array
124 ms for float, arry
time for array / time for vector = 90%