Bicoloring

https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=945

C++版本一

/*
*@Author:   STZG
*@Language: C++
*/
//#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
int co[N];
char str;
struct node{};
vector<int>G[N];
bool dfs(int u,int c){
    co[u]=c;
    for(int i=0,j=G[u].size();i<j;i++){
        int v=G[u][i];
        if(co[v]==c)return false;
        if(co[v]==0&&!dfs(v,-c))return false;
    }
    return true;
}
void init(){
    memset(co,0,sizeof(co));
    for(int i=0;i<n;i++)
        G[i].clear();
    flag=1;
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    while(~scanf("%d",&n)&&n){
        scanf("%d",&m);
        init();
        for(int i=1;i<=m;i++){
            scanf("%d%d",&u,&v);
            G[u].push_back(v);
            G[v].push_back(u);
        }
        for(int i=0; i<n; ++i) {
            if(co[i] == 0) {
                //如果顶点i还没被染色，则染成1
                if(!dfs(i,1)) {
                    flag=0;
                    break;
                }
            }
        }
        if(flag){
            printf("BICOLORABLE.\n");
        }else{
            printf("NOT BICOLORABLE.\n");
        }
    }

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}

C++版本二

/***********************************************/

int co[250];

struct node{
    int v;
    node(){}
    node(int _v):v(_v){}
};
vector<node>G[250];//邻接表法 

int fff=0;

void dfs(int now,int pre)
{
    if(~co[now])
    {
        if(co[pre]!=0) co[now]=-co[pre];
        else co[now]=1;//头结点染色
        //cout<<"co"<<G[now].size()<<endl;
        for(int i=0;i<G[now].size();i++)
        {
            if(fff==0 && G[now][i].v!=pre)
            dfs(G[now][i].v,now);
        }
    }
        
    else{//染过 
        if(co[now]==co[pre]){
            fff=1;
        }
    } 
    
}

int main()
{
    int n,m;
    while(cin>>n && n)
    {
        fff=0;
        mem0(G);
        cin>>m;
        for(int i=1;i<=m;i++){
            int a,b;
            cin>>a>>b;
            G[a].push_back(node(b));
            G[b].push_back(node(a)); 
        }
        mem0(co);
        dfs(0,0);
        //for(int i=0;i<n;i++) cout<<co[i]<<"tt";
        if(fff){
            cout<<"NOT BICOLORABLE."<<endl;
        }
        else cout<<"BICOLORABLE."<<endl;
    }
    return 0;
}

/*
3
3
0 1
1 2
2 0
3
2
0 1
1 2
9
8
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0

*/