Uva--10129 （欧拉回路，判连通）
2014-07-08 22:08:44
题意&思路：欧拉道路（无环）。思路：用并查集判连通，然后用入出度判断。
1 #include <cstdio> 2 #include <vector> 3 #include <cstring> 4 #include <iostream> 5 using namespace std; 6 7 int Case,n,fa[30],inc[100005],outc[100005]; 8 9 int Find(int x){ 10 if(fa[x] != x) return Find(fa[x]); 11 return fa[x]; 12 } 13 14 void Union(int a,int b){ 15 int x = Find(a); 16 int y = Find(b); 17 if(x != y) fa[y] = x; 18 } 19 20 int main(){ 21 int len; 22 char str[1005]; 23 scanf("%d",&Case); 24 while(Case--){ 25 scanf("%d",&n); 26 memset(inc,0,sizeof(inc)); 27 memset(outc,0,sizeof(outc)); 28 for(int i = 0; i < 26; ++i) 29 fa[i] = i; 30 31 for(int i = 0; i < n; ++i){ 32 scanf("%s",str); 33 len = strlen(str); 34 int a = (int)(str[0] - 'a'); 35 int b = (int)(str[len - 1] - 'a'); 36 if(fa[a] == -1) fa[a] = a; 37 if(fa[b] == -1) fa[b] = b; 38 Union(a,b); 39 40 outc[a]++; 41 inc[b]++; 42 } 43 int flag = 1,cntmin = 0,cntmax = 0,cnt = 0,setn = 0,ti; 44 for(int i = 0; i < 26; ++i) 45 if((inc[i] + outc[i]) && fa[i] == i) ++setn; 46 47 if(setn > 1) printf("The door cannot be opened.\n"); 48 else{ 49 for(int i = 0; i < 26; ++i){ 50 if(inc[i] != outc[i]){ //白书给出的严格条件 51 if(outc[i] - inc[i] == 1 && !cntmin) 52 cntmin = 1; 53 else if(inc[i] - outc[i] == 1 && !cntmax) 54 cntmax = 1; 55 else{ 56 flag = 0; 57 break; 58 } 59 } 60 } 61 if(flag) printf("Ordering is possible.\n"); 62 else printf("The door cannot be opened.\n"); 63 } 64 } 65 return 0; 66 }
