• UVA 11080 Place the Guards 二分图判定


    每个连通块分别取min{白色,黑色}

    //#pragma comment(linker, "/STACK:1024000000,1024000000")
    #include<cstdio>
    #include<cstring>
    #include<cstdlib>
    #include<algorithm>
    #include<iostream>
    #include<sstream>
    #include<cmath>
    #include<climits>
    #include<string>
    #include<map>
    #include<queue>
    #include<vector>
    #include<stack>
    #include<set>
    using namespace std;
    typedef long long ll;
    typedef unsigned long long ull;
    typedef pair<int,int> pii;
    #define pb(a) push(a)
    #define INF 0x1f1f1f1f
    #define lson idx<<1,l,mid
    #define rson idx<<1|1,mid+1,r
    #define PI  3.1415926535898
    template<class T> T min(const T& a,const T& b,const T& c) {
        return min(min(a,b),min(a,c));
    }
    template<class T> T max(const T& a,const T& b,const T& c) {
        return max(max(a,b),max(a,c));
    }
    void debug() {
    #ifdef ONLINE_JUDGE
    #else
    
        freopen("d:\in1.txt","r",stdin);
        freopen("d:\out1.txt","w",stdout);
    #endif
    }
    int getch() {
        int ch;
        while((ch=getchar())!=EOF) {
            if(ch!=' '&&ch!='
    ')return ch;
        }
        return EOF;
    }
    const int maxn=222;
    vector<int> g[maxn];
    int col[maxn];
    
    int num,all,res;
    bool dfs(int u,int color)
    {
        col[u]=color;
        all++;
        if(color==1)num++;
        for(int i=0;i<g[u].size();i++)
        {
            int v=g[u][i];
            if(!col[v])
            {if(!dfs(v,3-color))return false;}
            else if(col[u]==col[v])return false;
        }
        return true;
    }
    bool solve(int n)
    {
        memset(col,0,sizeof(col));
        res=0;
        for(int i=0;i<n;i++)
            if(!col[i])
            {
                num=0;
                all=0;
                if(!dfs(i,1))return false;
                int x=min(num,all-num);
                if(x==0)x++;
                res+=x;
            }
    
        return true;
    }
    int main()
    {
        int t;
        scanf("%d",&t);
        for(int ca=1;ca<=t;ca++)
        {
            int n,m;
            scanf("%d%d",&n,&m);
            for(int i=0;i<n;i++)
                g[i].clear();
            for(int i=0;i<m;i++)
            {
                int u,v;
                scanf("%d%d",&u,&v);
                g[u].push_back(v);
                g[v].push_back(u);
            }
            int flag=solve(n);
            printf("%d
    ",flag?res:-1);
        }
        return 0;
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/BMan/p/3619314.html
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