算法竞赛入门经典习题与解答-第一章_算法竞赛入门经典 习题与解答pdf

1.1.1 排序性能问题

 C语言的函数qsort，C++中的sort（直接传入排序函数）以及传入functor对象的sort函数代码以及时间。

#include<bits/stdc++.h>
using namespace std;
#define _for(i,a,b) for( int i=(a); i<(b); ++i)
const int N = 10000000;
struct TS{
    int a,b,c;
};
inline bool cmp (const TS&t1, const TS&t2){
    if(t1.a!=t2.a)return t1.a<t2.a;
    if(t1.b!=t2.b)return t1.b<t2.b;
    return t1.c<t2.c;
}
 
int cmp4qsort(const void * a, const void * b){
    TS *t1 = (TS*)a, *t2 = (TS*)b;
    if(t1->a != t2->a) return t1->a - t2->a;
    if(t1->b != t2->b) return t1->b - t2->b;
    return t1->c - t2->c;
}
struct cmpFunctor{
    inline bool operator() (const TS& t1, const TS& t2){
        if(t1.a != t2.a) return t1.a < t2.a;
        if(t1.b != t2.b) return t1.b < t2.b;
        return t1.c < t2.c;
    }
};
 
TS tss[N];
 
void genData(){
    _for(i , 0, N){
        tss[i].a = rand();
        tss[i].b = rand();
        tss[i].c = rand();
    }
}
 
int main()
{
    srand(time(NULL));
 
    genData();
    clock_t start = clock();
    sort(tss, tss+N, cmp);
    printf("sort by funtion pointer : %ld\n",clock() - start);
 
    genData();
    start = clock();
    sort(tss, tss+N, cmpFunctor());
    printf("sort by functor : %ld\n",clock() - start);
 
    genData();
    start = clock();
    qsort(tss, N, sizeof(TS), cmp4qsort);
    printf("qso