HDU 5971 Wrestling Match(染色+暴力)

来源：互联网发布：av淘宝2017在线编辑：程序博客网时间：2024/05/21 10:09

题目分析

主要的策略就是如果有已经确定的点，那么很明显沿着这条边直接跑就可以了，判断其相连的所有点时good player 还是 bad player，如果所有已经明确了的所有已经明确了的点都没有相邻边，那么直接找一个没有被标记过的点跑一下就可以了。

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int maxn = 1005;struct Edge{    int to, next;}e[maxn*20];int head[maxn], color[maxn], tot;void addedge(int from, int to){    e[tot].to = to;    e[tot].next = head[from];    head[from] = tot++;}bool dfs(int u, int fa){    for(int i = head[u]; i != -1; i = e[i].next){        int v = e[i].to;        if(v == fa) continue;        if(color[v] == color[u]) return false;        if(!color[v]){            color[v] = 3 - color[u];            if(!dfs(v, u)) return false;        }    }    return true;}void init(){    tot = 0;    memset(head, -1, sizeof(head));    memset(color, 0, sizeof(color));}int main(){    int n, m, x, y;    while(scanf("%d%d%d%d", &n, &m, &x, &y) != EOF){        init();        int from, to;        for(int i = 0; i < m; i++){            scanf("%d%d", &from, &to);            addedge(from, to);            addedge(to, from);        }        int xx;        int flag = true, cnt = 1;        for(int i = 0; i < x; i++){            scanf("%d", &xx);            if(!color[xx]){                color[xx] = 1;                if(head[xx] != -1) cnt = 0;                flag = flag&&dfs(xx, -1);            }            else if(color[xx] == 2) flag = false;        }        for(int i = 0; i < y; i++){            scanf("%d", &xx);            if(!color[xx]){                color[xx] = 2;                if(head[xx] != -1) cnt = 0;                flag = flag&&dfs(xx, -1);            }            else if(color[xx] == 1) flag = false;        }        if(!flag){            printf("NO\n");            continue;        }        else{            if(cnt){                for(int i = 1; i <= n; i++)                    if(!color[i]){                        color[i] = 1;                        flag = flag&&dfs(i, -1);                        break;                    }                for(int i = 1; i <= n; i++)                    if(!color[i]){ flag = false; break; }            }            else{                for(int i = 1; i <= n; i++)                    if(!color[i]){ flag = false; break;}            }        }        if(flag) printf("YES\n");        else printf("NO\n");    }    return 0;}

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