UVALive 6604 Airport Sort 【归并排序】【逆序数】

//从归并排序到数列的逆序数对
#include <stdio.h>
#include <iostream>
using namespace std;

int g_nCount = 0;
void mergearray(int a[], int first, int mid, int last, int temp[])
{
    int i = first, j = mid + 1;
    int m = mid,   n = last;
    int k = 0;

    while (i <= m && j <= n) //a[i] 前面的数  a[j] 后面的数
    {
        if (a[i] <= a[j])temp[k++] = a[i++];
        else{
            temp[k++] = a[j++];//a[j]和前面每一个数都能组成逆序数对
            g_nCount += m - i + 1;
        }
    }
    while (i <= m) temp[k++] = a[i++];
    while (j <= n) temp[k++] = a[j++];
    for (i = 0; i < k; i++) a[first + i] = temp[i];
}
void mergesort(int a[], int first, int last, int temp[])
{
    if (first < last)
    {
        int mid = (first + last) / 2;
        mergesort(a, first, mid, temp);    //左边有序
        mergesort(a, mid + 1, last, temp); //右边有序
        mergearray(a, first, mid, last, temp); //再将二个有序数列合并
    }
}

bool MergeSort(int a[], int n)
{
    int *p = new int[n];
    if (p == NULL)
        return false;
    mergesort(a, 0, n - 1, p);
    delete[] p;
    return true;
}

int main ()
{
    int  CASE,T,k,a[1005];
    scanf("%d",&CASE);
    for(int cas = 1; cas<=CASE; cas++){
        scanf("%d %d",&T,&k);
        g_nCount = 0;
        int count2=0;
        for(int i = 0; i < T; i++){
            scanf("%d",&a[i]),a[i]=(a[i]-1)/k + 1;
            int m = i / k + 1;
            if(m>a[i])
                count2=max(count2,i+1-(k*a[i]+1));
            
            else if(m<a[i])
                count2=max(count2,k*(a[i]-1)+1-(i+1));
            
        }
        MergeSort(a,T);
        printf("Case %d: %d\n",cas,g_nCount-count2);
    }
}