UVA6588 - Crane

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Regionals 2013 >>Europe - Central

6588 - Crane

题意：给定一组无序数，从1-n，要求排序，排序的要求是选定一个区间[a，b]，则这个区间的前一半和后一半互换位置，a到b有偶数个数，问交换几次。

解题思路：由于数字个数不多，可以枚举1-n个位置，枚举第i个位置，就找到第i个点所在点的位置，如果可以直接交换就交换，如果不能就一半一半交换。

#include <stdio.h>#include <iostream>#include <string.h>#include <math.h>#include <algorithm>#include <stdlib.h>#include <queue>#include <vector>#include <map>using namespace std;const int inf = 0x3f3f3f3f;const int Max = 10100;typedef long long int LL;int a[Max],vis[Max], n, rr[531500], ll[531500];int cut;void exch(int l, int r){    int i, t;    int mid = r-l;    ll[cut] = l;    rr[cut++] = r+mid-1;    //printf("%d %d\n", l, r+mid-1);    for(i = l; i < r; i++)    {        t = a[i];        a[i] = a[i+mid];        a[i+mid] = t;        t = vis[a[i]];        vis[a[i]] = vis[a[i+mid]];        vis[a[i+mid]] = t;    }    /*for(i = 1; i <= n; i++)    {        cout<<a[i]<<" ";    }    cout<<endl;*/}int main(){    int i, pos, j;    int K;    scanf("%d", &K);    while(K--)    {        scanf("%d",&n);        cut = 0;        for(i = 1; i <= n; i++)        {            scanf("%d",&a[i]);            vis[a[i]] = i;        }        for(i = 1; i <= n; i++)        {            if(vis[i] == i)                continue;            pos = vis[i];            while(a[i] != i)            {                int end = i+(pos-i)*2-1;                if(end <= n)                {                    exch(i, pos);                }                else                {                    int mid = pos - i +1;                    if(mid%2 == 0)                    {                        exch(i, i + mid/2);                        pos = vis[i];                    }                    else                    {                        exch(i+1, i+mid/2+1);                        pos = vis[i];                    }                }            }        }        printf("%d\n", cut);        for(i = 0; i < cut; i++)        {            printf("%d %d\n", ll[i], rr[i]);        }    }    return 0;}

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