数组中的逆序对

#include <iostream>
using namespace std;

/*********************************
func:合并有序的相邻字数组，并统计逆序对数
para:a:左有序字数组；lenA:左有序字数组长度；b:右有序字数组；lenB:右有序字数组长度；inversePairsCount：相邻有序字数组a和b之间存在的逆序对数
return:void
*********************************/
void mergeAndCount(int* a,int lenA,int* b,int lenB,int& inversePairsCount){
    int* temp=new int[lenA+lenB];
    int index=0;
    memset(temp,0,sizeof(int)*(lenA+lenB));
    int* aPtr=a;
    int* bPtr=b;
    while(aPtr<a+lenA&&bPtr<b+lenB){
        if(*aPtr<=*bPtr){
            temp[index++]=*(aPtr++);
        }
        else{ //A大于B的元素，将B的元素与A的当前及后面的元素比较大小，判断逆序对数
            for(int* aNow=aPtr;aNow<a+lenA;++aNow){
                if(*aNow>*bPtr)
                    ++inversePairsCount;
            }
            temp[index++]=*(bPtr++);
        }
    }
    while(aPtr<a+lenA)
        temp[index++]=*(aPtr++);
    while(bPtr<b+lenB)
        temp[index++]=*(bPtr++);
    memcpy(a,temp,sizeof(int)*(lenA+lenB));
    delete[] temp;
}

/*******************************************
func:统计给定数组A中存在逆序对数
para:A:待统计数组；len:数组A的长度；inversePairsCount：逆序对数
ret:void
*******************************************/
void inverseCount(int A[],int len,int& inversePairsCount){
    int leftLen=len/2;
    if(leftLen>0){
        inverseCount(A,leftLen,inversePairsCount);
        inverseCount(A+leftLen,len-leftLen,inversePairsCount);
        mergeAndCount(A,leftLen,A+leftLen,len-leftLen,inversePairsCount);
    }
}

int main(){
    int A[]={7,5,6,4,1};
    int inversePairsCount=0;
    inverseCount(A,5,inversePairsCount);
    cout<<"inversePairsCount:"<<inversePairsCount<<endl;
    for(int i=0;i<5;++i)
        cout<<A[i]<<" ";
    getchar();
}