两道有关欧拉回路的例题
POJ1300-Door Man
//判定是否存在从某点到0点的欧拉回路
//Time:0Ms Memory:116K
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std; #define MAX 25
int st, n;
int door[MAX]; int main()
{
char s[120];
while (scanf("%s", s), strcmp(s, "ENDOFINPUT"))
{
memset(door, 0, sizeof(door));
int doors = 0;
scanf("%d%d", &st, &n);
gets_s(s, 120);
for (int i = 0; i < n; i++)
{
gets_s(s, 120);
int num, k = 0;
while (sscanf(s + k, "%d", &num) == 1)
{
doors++;
door[num]++;
door[i]++;
while (s[k] == ' ') k++;
while (s[k] && s[k] != ' ') k++;
}
}
gets_s(s, 120);
int odd = 0;
for (int i = 0; i < n; i++)
odd += door[i] % 2 == 1;
if (odd == 0 && st == 0)
printf("YES %d\n", doors); //无奇度节点
else if (odd == 2 && st && door[st] % 2 && door[0] % 2)
printf("YES %d\n", doors); //两个奇度节点
else printf("NO\n");
}
return 0;
}
POJ1386-Plays on Words
//判断能否使给定的词组前后接龙
//Time:344Ms Memory:120K
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std; #define MAX 28
#define MAXS 1005
#define MAXN 100005 int n;
char s[MAXS];
int in[MAX], out[MAX];
int fa[MAX]; int find(int x)
{
return fa[x] < 0 ? x : find(fa[x]);
} int Union(int r1, int r2)
{
r1 = find(r1); r2 = find(r2);
if (r1 == r2) return r1;
int tmp = fa[r1] + fa[r2];
if (fa[r1] > fa[r2])
{
fa[r1] = r2;
fa[r2] = tmp;
return r2;
}
else {
fa[r2] = r1;
fa[r1] = tmp;
return r1;
}
} int main()
{
//freopen("words.in", "r", stdin);
int T;
scanf("%d", &T);
while (T--) {
memset(in, 0, sizeof(in));
memset(out, 0, sizeof(out));
memset(fa, -1, sizeof(fa)); int pa;
scanf("%d", &n);
while (n--) {
scanf("%s", s);
int i = s[strlen(s) - 1] - 'a';
int o = s[0] - 'a';
out[o]++; in[i]++;
pa = Union(i, o);
} int odd = 0;
bool connect = true;
bool A = false, B = false;
for (int i = 0; i < 26; i++)
{
if (!in[i] && !out[i]) continue;
if (pa != find(i)) {
connect = false; break;
}
if (in[i] - out[i] != 0)
{
odd++;
if (in[i] - out[i] == 1) A = true;
if (in[i] - out[i] == -1) B = true;
}
}
if (connect && ((odd == 2 && A && B) || odd == 0))
printf("Ordering is possible.\n");
else printf("The door cannot be opened.\n");
} return 0;
}