POJ 2299：Ultra-QuickSort

Ultra-QuickSort

Time Limit: 7000MS		Memory Limit: 65536K
Total Submissions: 39397		Accepted: 14204

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

Sample Output

6

0

归并排序。

另外，此题有一坑就是结果会超int32；

详细能够參考：点击打开链接

我写的代码例如以下：

#include<cstdio>

#include<stdlib.h>

#include<cstring>

#include<algorithm>

#include<iostream>

using namespace std;

const int M = 500000 + 5;

int n, A[M], T[M], i;

long long merge_sort(int l, int r, int *A)

{

    if (r - l < 1) return 0;

    int mid = (l + r) / 2;

    long long ans = merge_sort(l, mid, A) + merge_sort(mid + 1, r, A);

    i = l;

    int p = l, q = mid + 1;

    while (p <= mid && q <= r)

    {

        if(A[p] <= A[q])

            T[i++] = A[p++];

        else

        {

            ans += (mid + 1 - p);

            T[i++] = A[q++];

        }

    }

    while (p <= mid) T[i++] = A[p++];

    while (q <= r) T[i++] = A[q++];

    for (int j = l; j <= r; j++)

        A[j] = T[j];

    return ans;

}

int main()

{

    int n;

    while(scanf("%d", &n) && n)

    {

        for(int j=0; j<n; j++)

            scanf("%d", &A[j]);

       printf("%lld\n", merge_sort(0, n - 1, A));

    }

    return 0;

}

巴特西

POJ 2299：Ultra-QuickSort

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