UVa 10596 - Morning Walk

来源：互联网发布：linux crontab 权限编辑：程序博客网时间：2024/06/05 19:09

題目：Kamal早上散步，發現有很多條路，問能否每條路走一次回到原點。

分析：圖論，歐拉迴路，并查集。判斷是否存在歐拉迴路。

歐拉迴路存在條件：1.有邊的點度數為偶數，2.右邊的點構成的圖聯通。

說明：╮(╯▽╰)╭。

#include <cstdlib>#include <cstring>#include <cstdio>#define NODE_SIZE 202#define EDGE_SIZE 10001int degree[NODE_SIZE];typedef struct _edge{int point1;int point2;}edge;edge E[EDGE_SIZE];//union_setint sets[NODE_SIZE];int rank[NODE_SIZE];void set_inital(int a, int b){for (int i = a; i <= b; ++ i) {rank[i] = 0;sets[i] = i;}}int set_find(int a){if (a != sets[a])sets[a] = set_find(sets[a]);return sets[a];}void set_union(int a, int b){if (rank[a] < rank[b])sets[a] = b;else {if (rank[a] == rank[b])rank[a] ++;sets[b] = a;}}//end_union_setint euler(int n, int m){memset(degree, 0, sizeof(degree));set_inital(0, n);for (int i = 0; i < m; ++ i) {int A = set_find(E[i].point1);int B = set_find(E[i].point2);if (A != B) set_union(A, B);degree[E[i].point1] ++;degree[E[i].point2] ++;}int ans = 0, flag = 0;for (int i = 0; i < n; ++ i) {if (degree[i]) ans += (sets[i]==i);if (degree[i]%2) flag = 1;}return (ans == 1 && !flag);}int main(){int n, m;while (~scanf("%d%d",&n,&m)) {for (int i = 0; i < m; ++ i)scanf("%d%d",&E[i].point1,&E[i].point2);if (euler(n, m))printf("Possible\n");else printf("Not Possible\n");}return 0;}

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