POJ 2438 Children's Dining(哈密顿回路)

传送门

题解：建立这个图的反图，然后进行哈密顿回路

#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>

using namespace std;
typedef long long LL;
const int maxN = 400;

inline void reverse(int arv[maxN + 7], int s, int t){
    int temp;
    while(s  < t){
        temp = arv[s];
        arv[s] = arv[t];
        arv[t] = temp;
        s++;
        t--;
    }
}

void Hamilton(int ans[maxN + 7], bool map[maxN + 7][maxN + 7], int n){
    int s = 1, t;
    int ansi = 2;
    int i, j;
    int w;
    int temp;
    bool visit[maxN + 7] = {false};
    for(i = 1; i <= n; i++) if(map[s][i]) break;
    t = i;
    visit[s] = visit[t] = true;
    ans[0] = s;
    ans[1] = t;
    while(true){
        while(true){
            for(i = 1; i <= n; i++){
                if(map[t][i] && !visit[i]){
                    ans[ansi++] = i;
                    visit[i] = true;
                    t = i;
                    break;
                }
            }
            if(i > n) break;
        }
        w = ansi - 1;
        i = 0;
        reverse(ans, i, w);
        temp = s;
        s = t;
        t = temp;
        while(true){
            for(i = 1; i <= n; i++){
                if(map[t][i] && !visit[i]){
                    ans[ansi++] = i;
                    visit[i] = true;
                    t = i;
                    break;
                }
            }
            if(i > n) break;
        }
        if(!map[s][t]){
            for(i = 1; i < ansi - 2; i++)
                if(map[ans[i]][t] && map[s][ans[i + 1]])break;
            w = ansi - 1;
            i++;
            t = ans[i];
            reverse(ans, i, w);
        }
        if(ansi == n) return;
        for(j = 1; j <= n; j++){
            if(visit[j]) continue;
            for(i = 1; i < ansi - 2; i++)if(map[ans[i]][j])break;
                if(map[ans[i]][j]) break;
        }
        s = ans[i - 1];
        t = j;
        reverse(ans, 0, i - 1);
        reverse(ans, i, ansi - 1);
        ans[ansi++] = j;
        visit[j] = true;
    }
}

int main(){
    int N, M;
    while(~scanf("%d%d", &N, &M) && (N || M)){
        N *= 2;
        bool map[maxN + 7][maxN + 7] = {0};
        int ans[maxN + 7] = {0};
        int ansi = 0;
        for(int i = 0; i <= N; i++)
            for(int j = 0; j <= N; j++)
                i == j ? map[i][j] = map[j][i] = 0 : map[i][j] = map[j][i] = 1;
        memset(ans, 0, sizeof(ans));
        for(int i = 1; i <= M; i++){
            int u, v;
            scanf("%d%d", &u, &v);
            map[u][v] = map[v][u]= 0;
        }
        Hamilton(ans, map, N);
        for(int i = 0; i < N; i++)
            printf(i == 0 ? "%d":" %d", ans[i]);
        printf("\n");

    }
    return 0;
}