hdoj Sort it 2689 （归并排序）

Sort it

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3498    Accepted Submission(s): 2536

Problem Description

You want to processe a sequence of n distinct integers by swapping two adjacent sequence elements until the sequence is sorted in ascending order. Then how many times it need.
For example, 1 2 3 5 4, we only need one operation : swap 5 and 4.

Input

The input consists of a number of test cases. Each case consists of two lines: the first line contains a positive integer n (n <= 1000); the next line contains a permutation of the n integers from 1 to n.

Output

For each case, output the minimum times need to sort it in ascending order on a single line.

Sample Input

31 2 34 4 3 2 1 

Sample Output

06
 
#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;int a[1010];int b[1010];int n,cnt;void merge(int a[],int s,int m,int e){int i=s,j=m+1,k=s;while(i<=m&&j<=e){if(a[i]<=a[j])b[k++]=a[i++];else{cnt+=j-k;b[k++]=a[j++];}}while(i<=m)b[k++]=a[i++];while(j<=e)b[k++]=a[j++];for(i=s;i<=e;i++)a[i]=b[i];}void mergesort(int a[],int s,int e){if(s<e){int m=(s+e)/2;mergesort(a,s,m);mergesort(a,m+1,e);merge(a,s,m,e);}}int main(){int i,j,mm;while(scanf("%d",&n)!=EOF){for(i=1;i<=n;i++)scanf("%d",&a[i]);cnt=0;mergesort(a,1,n);printf("%d\n",cnt);}return 0;}