算法竞赛入门经典 快速排序和并归排序

/*快速排序 和 归并排序求逆序对*/#include<cstring>#include<cstdio>#include<cstdlib>#include<iostream>#include<cmath>#include <algorithm>using namespace std;const int MAX = 500;int A[MAX];int n;int tot;int T[MAX];int merge_sort(int p, int q){    int cnt = 0;    if(q-p > 1) {        int m = p + (q-p)/2;        cnt += merge_sort(p, m);        cnt += merge_sort(m, q);        int x = p, y = m, i = p;        while(x<m || y<q) {            tot++;            if(y>=q || (x<m && A[x]<=A[y])) {                T[i++] = A[x++];            } else {                cnt += (m-x);                T[i++] = A[y++];            }        }        for(int i=p; i<q; i++) {            tot++;            A[i] = T[i];        }    }    return cnt;}int patition(int p, int q){    int key = A[q-1];    int j=p-1;    for(int i=p; i<q-1; i++) {        tot++;        if(A[i] < key) {            swap(A[i], A[++j]);        }    }    swap(A[++j], A[q-1]);    return j;}void quick_sort(int p, int q){    if(q-p > 1) {        int m = patition(p, q);        quick_sort(p, m);        quick_sort(m+1, q);    }}int main(){    #ifndef ONLINE_JUDGE    freopen("in.txt", "r", stdin);    //freopen("merge_sort.txt", "w", stdin);    #endif    while(scanf("%d", &n) == 1) {        for(int i=0; i<n; i++) {            scanf("%d", &A[i]);        }        printf("%d: ", n);        for(int i=0; i<n; i++) {            printf("%d ", A[i]);        }        printf("\n");        tot = 0;        //quick_sort(0, n);        //printf("time:%d\n", tot);        int ret = merge_sort(0, n);        printf("re_order: %d\n", ret);        printf("time:%d\n", tot);        for(int i=0; i<n; i++) {            printf("%d ", A[i]);        }    }    return 0;}