题目链接 

 

解题思路

需要判断图是否连通 且 只有一个连通分量

注意只有0 0的情况。

 

代码

#include
     
      #include
      
       #define SET_SIZE 100010int s[SET_SIZE];bool vis[SET_SIZE];void MakeSet(int n){	for(int i=1; i<=n; i++) s[i] = i;}int FindFather(int x){	if(s[x] != x)		s[x] = FindFather(s[x]);	return x;}void UnionSet(int fx, int fy){	s[fx] = fy;}int main(){	int x, y;	scanf("%d%d", &x, &y);	while(!(x == -1 && y == -1)) {		bool flag = false;		int count = 0;		int vNum = 0, edgeNum = 0;		MakeSet(SET_SIZE);		memset(vis, 0, sizeof(vis));		while(!(x == 0 && y == 0)) {			count++;			if(!vis[x]) { vNum++; vis[x] = true; }			if(!vis[y]) { vNum++; vis[y] = true; }			if(!flag) {				int fx = FindFather(x);				int fy = FindFather(y);				if(fx == fy) flag = true;				else {					UnionSet(fx, fy);					edgeNum++;				}			}			scanf("%d%d", &x, &y);		}		if(count == 0) printf("Yes\n");		else{			if(!flag && vNum == edgeNum + 1) printf("Yes\n"); 			else printf("No\n");		}		scanf("%d%d", &x, &y);	}	return 0;}