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  • Codeforces 500B. New Year Permutation[连通性]

    B. New Year Permutation
    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    User ainta has a permutation p1, p2, ..., pn. As the New Year is coming, he wants to make his permutation as pretty as possible.

    Permutation a1, a2, ..., an is prettier than permutation b1, b2, ..., bn, if and only if there exists an integer k (1 ≤ k ≤ n) where a1 = b1, a2 = b2, ..., ak - 1 = bk - 1 and ak < bk all holds.

    As known, permutation p is so sensitive that it could be only modified by swapping two distinct elements. But swapping two elements is harder than you think. Given an n × n binary matrix A, user ainta can swap the values of pi and pj (1 ≤ i, j ≤ ni ≠ j) if and only if Ai, j = 1.

    Given the permutation p and the matrix A, user ainta wants to know the prettiest permutation that he can obtain.

    Input

    The first line contains an integer n (1 ≤ n ≤ 300) — the size of the permutation p.

    The second line contains n space-separated integers p1, p2, ..., pn — the permutation p that user ainta has. Each integer between 1 and n occurs exactly once in the given permutation.

    Next n lines describe the matrix A. The i-th line contains n characters '0' or '1' and describes the i-th row of A. The j-th character of the i-th line Ai, j is the element on the intersection of the i-th row and the j-th column of A. It is guaranteed that, for all integers i, j where 1 ≤ i < j ≤ nAi, j = Aj, i holds. Also, for all integers i where 1 ≤ i ≤ nAi, i = 0 holds.

    Output

    In the first and only line, print n space-separated integers, describing the prettiest permutation that can be obtained.

    Examples
    input
    7
    5 2 4 3 6 7 1
    0001001
    0000000
    0000010
    1000001
    0000000
    0010000
    1001000
    output
    1 2 4 3 6 7 5
    input
    5
    4 2 1 5 3
    00100
    00011
    10010
    01101
    01010
    output
    1 2 3 4 5
    Note

    In the first sample, the swap needed to obtain the prettiest permutation is: (p1, p7).

    In the second sample, the swaps needed to obtain the prettiest permutation is (p1, p3), (p4, p5), (p3, p4). 

    permutation p is a sequence of integers p1, p2, ..., pn, consisting of n distinct positive integers, each of them doesn't exceed n. The i-th element of the permutation p is denoted as pi. The size of the permutation p is denoted as n.


    位置的swap关系可以构成一个连通块

    每一个连通块贪心就行了

    实现上,可以用并查集维护,然后对于1到n每一个位置找连通块中最小的

    //
    //  main.cpp
    //  cf500b
    //
    //  Created by Candy on 9/16/16.
    //  Copyright © 2016 Candy. All rights reserved.
    //
    
    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <algorithm>
    using namespace std;
    const int N=305;
    int n,p[N],a[N][N],ans[N];
    char tmp[N];
    int fa[N];
    int find(int x){return x==fa[x]?x:fa[x]=find(fa[x]);}
    int main(int argc, const char * argv[]) {
        scanf("%d",&n);
        for(int i=1;i<=n;i++) scanf("%d",&p[i]),fa[i]=i;
        for(int i=1;i<=n;i++){
            scanf("%s",tmp+1);
            for(int j=1;j<=n;j++)
                if(tmp[j]=='1'){
                    int x=find(i),y=find(j);
                    if(x!=y) fa[y]=x;
                }
        }
        for(int i=1;i<=n;i++){
            int mn=i;
            for(int j=i+1;j<=n;j++)
                if(find(i)==find(j)&&p[j]<p[mn]) mn=j;
            swap(p[mn],p[i]);
            printf("%d ",p[i]);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/candy99/p/5877689.html
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