pku 2513 Colored Sticks 欧拉通路问题

这题的本质是欧拉通路的思想.

不过还需要并查集来判断是否是联通图, 用trie存储所有的字符串.

 

#include <iostream>using namespace std;#define swap(i,j) {int temp=i; i = j; j = temp;}struct Node{int index;Node* arr[26];Node(){index = -1;memset(arr, 0, sizeof(arr));}};int parent[500001];int degree[500001];Node* root = new Node(); //根节点int words_count = 0; //不同的单词的总的个数int get_num(char* str){Node* p = root;while(*str){int index = *str-'a';if(!p->arr[index])p->arr[index] = new Node();p = p->arr[index];str++;}if(p->index == -1)p->index = words_count++;return p->index;}int ufset_find(int i){int p = i;while(parent[p] >= 0)p = parent[p];while(i != p){parent[i] = p;i = parent[i];}return p;}void ufset_union(int i, int j){i = ufset_find(i);j = ufset_find(j);if(i == j)return;if(parent[i] < parent[j])swap(i, j);parent[i] += parent[j]; //注意这两行的先后顺序!parent[j] = i;}int main(){memset(parent, -1, sizeof(parent));memset(degree, 0, sizeof(degree));char str1[11], str2[11];while(scanf("%s %s", str1, str2) != EOF){int i = get_num(str1);int j = get_num(str2);degree[i]++;degree[j]++;ufset_union(i, j);}if(!words_count){printf("Possible/n");return 0;}if(parent[ufset_find(0)] + words_count){printf("Impossible/n");return 0;}int cnt = 0;for(int i = 0; i < words_count; ++i)if(degree[i]&1)cnt++;if(cnt == 2 || cnt == 0)printf("Possible/n");elseprintf("Impossible/n");return 0;}