UVA10054

#include<stdio.h>
#include<string.h>
#define N 100 

int map[N][N], vis[N], degree[N]; 
int n, m, a, b, t = 0, count; 

void dfs(int u) {
    vis[u] = 1;
    count++;    
    for (int i = 1;i <= 51; i++)
        if (!vis[i] && map[u][i]) {
            dfs(i);         
        }
    return;
}//深度遍历

int circuit() {
    for(int i = 1;i <= 51; i++)
        if(degree[i] % 2 != 0)
            return 0;
    return 1;
}//判断是否连通

void euler(int u) {
    for(int i = 1;i < 51; i++)
        if(map[u][i]) {
            map[u][i]--;
            map[i][u]--;    
            euler(i);   
            printf("%d %d\n", i, u);    
        }   
    return;
}//递归，将已经递归到头的那个数输出


int main(){
    scanf("%d", &n);
    while(n--){
        int k = 0, cnt = 0, flag = 0;   
        scanf("%d", &m);    
        memset(map, 0, sizeof(map));    
        memset(vis, 0, sizeof(vis));    
        memset(degree, 0, sizeof(degree));      

        for (int i = 0;i < m; i++) {
            scanf("%d %d", &a, &b); 
            map[a][b]++;    
            map[b][a]++;//记录边数
            degree[a]++;
            degree[b]++;//记录每一个的度数
        }

        for (int j = 0;j < 51; j++) {
            if(degree[j]) {
                cnt++;
                k = j;  
            }   
        }

        printf("Case #%d\n", ++t);  
        if (!circuit()) {
            flag = 1;   
            printf("some beads may be lost\n"); 

        }
        count = 0;  
        if (!flag) {   
            dfs(k); 
            if (count != cnt)        
                printf("some beads may be lost\n"); 
            else    
                euler(k);   
        }   
        if (n != 0)  
            printf("\n");   
    }       
    return 0;
}