Ultra-QuickSort poj2299 （归并排序 求逆序数对）

Ultra-QuickSort

Time Limit: 7000MS Memory Limit: 65536KTotal Submissions: 57649 Accepted: 21298

Description

In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. For the input sequence
9 1 0 5 4 ,
Ultra-QuickSort produces the output
0 1 4 5 9 .
Your task is to determine how many swap operations Ultra-QuickSort needs to perform in order to sort a given input sequence.

Input

The input contains several test cases. Every test case begins with a line that contains a single integer n < 500,000 -- the length of the input sequence. Each of the the following n lines contains a single integer 0 ≤ a[i] ≤ 999,999,999, the i-th input sequence element. Input is terminated by a sequence of length n = 0. This sequence must not be processed.

Output

For every input sequence, your program prints a single line containing an integer number op, the minimum number of swap operations necessary to sort the given input sequence.

Sample Input

59105431230

Sample Output

60

///2299 MergeSort#include <iostream>#include <cstdio>using namespace std;const int maxn=500010;int num[maxn],temp[maxn];long long sum;void Merge(int low,int mid,int high){    int i=low;    int j=mid+1;    int cnt=1; ///cnt 多加了一个    while(i<=mid && j<=high)    {        if(num[i] < num[j]) ///防止相等的时候计算逆序对        {            temp[cnt++]=num[i++];        }        else        {            temp[cnt++]=num[j++];            sum+=mid+1-i;            ///左边的元素比右边的大，那么左边剩下的没比完的元素和这个右边的元素都构成了逆序对            /// 12354  5和4 比较; 逆序对就是1  12543 5和4 然后就是12453 4和3        }    }    while(i<=mid)    {        temp[cnt++]=num[i++];    }    while(j<=high)    {        temp[cnt++]=num[j++];    }    for (i=1;i<cnt;i++) /// 从low开始复制回去    {        num[low+i-1]=temp[i];    }}void msort(int low,int high){    int mid;    if (low<high)    {        mid=(low+high)/2;        msort(low,mid);        msort(mid+1,high);        Merge(low,mid,high);    }}int main(){    int i,n;    while(cin>>n && n)    {    sum=0;        for(i=1; i<=n; i++)        {            scanf("%d",&num[i]);        }        msort(1,n);        printf("%lld\n",sum);    }    return 0;}