归并排序、求逆序对归并排序(mergesort)
归并排序(mergesort)归并排序采用分治的思想：先将#include<iostream>using namespace std;int a[10001];int b[10001];int ans;void mergesort(int l,int r){ if(l == r) return ; int mid=(l+r)/2; mergesort(l,mid); mergesort(mid+1,r); int i=l,j=mid+1,p=l; while(i
