归并排序 简单版

下面是我整理刘汝佳算法的代码，按照自己格式改了改，还有另一种比较适合自己

#include<stdio.h>
#include<string.h>
#include<math.h>
#include <queue>
#include <iostream>
#include<algorithm>
using namespace std;
const int N=10000+2;
int A[N];
int T[N];
void Merge_sort(int l,int r)
{
    if (r-l>1)
    {
        int mid=l+(r-l)/2;
        int p=l,i=l,q=mid;
        Merge_sort(l,mid);
        Merge_sort(mid,r);
        while (p<mid||q<r)
        {
            if (q>=r||(p<mid&&A[p]<=A[q]))
                T[i++]=A[p++];
            else
                T[i++]=A[q++];
        }
        for (i=l;i<r;i++)
            A[i]=T[i];
    }
}

这是算法书里面的求逆序对的解法，但是它的合并比较好理解，用了三个循环

#include<stdio.h>
#include<string.h>
#include<math.h>
#include <queue>
#include <iostream>
#include<algorithm>
using namespace std;
const int N=10000+2;
int A[N];
int B[N];
int r;
void merge(int l, int h) {
    if (l >= h-1) {
        return;
    }

    int m = l + (h - l) / 2;
    merge(l, m);
    merge(m, h);

    int i = l, j = m, k = l;
    while (i < m && j < h) {
        if (A[i] > A[j]) {
            B[k++] = A[j++];
           r += m - i;
        } else {
            B[k++] = A[i++];
        }
    }
    if (i < m) {
        for (; i < m; i++) {
            B[k++] = A[i++];
        }
    }
    if (j < h) {
        for (; j < h; j++) {
            B[k++] = A[j++];
        }
    }
    for (int x = l; x < h; x++) {
        A[x] = B[x];
    }
}

int main() {
    int n;
    while (cin>>n)
    {
        r=0;
    for (int i=0;i<n;i++)
        cin>>A[i];
           merge(0, n);
    for (int i = 0; i < n; i++) {
        cout << A[i] << " ";
    }
    cout << endl;
    cout << "reverse pair number is " << r << endl;
    }
}