POJ 2513 Colored Sticks——字典树+并查集+欧拉回路

比较综合的一道题，套用字典树以及并查集模板。

注意：

1.字典树应该有提供单词编号的功能，这也是解题必须的要素

2.输入为空返回0，这个跟写法有关，我的写法不用特殊判断

3注意各种细节，本题综合性较强，代码量较大，稍不留神就会出现细节错误，注意及时调试

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#include <string>#define ID(x) x - 'a'using namespace std;const int maxn = 1e6;int next;struct Trie {    int next[26];    int val;}tree[maxn];int add() {    memset(&tree[next], 0, sizeof(Trie));    return next++;}void Insert(char *s) {    int cur = 0, len = strlen(s);    for (int i = 0; i < len; i++) {        int id = ID(s[i]);        if (!tree[cur].next[id]) {            tree[cur].next[id] = add();        }        cur = tree[cur].next[id];    }    tree[cur].val++;}int Find(char *s) {    int rt = 0, len = strlen(s);    for (int i = 0; i < len; i++) {        int id = ID(s[i]);        if (!tree[rt].next[id]) return 0;        rt = tree[rt].next[id];    }    if (tree[rt].val) return rt;    return 0;}int par[maxn], ran[maxn];void init() {    for (int i = 0; i < maxn; i++) {        par[i] = i, ran[i] = 0;    }}int seek(int x) {    if (par[x] == x) return x;    else return par[x] = seek(par[x]);}void unite(int x, int y) {    x = seek(x), y = seek(y);    if (x == y) return;    if (ran[x] < ran[y]) par[x] = y;    else {        par[y] = x;        if (ran[x] == ran[y]) ran[x]++;    }}int du[maxn] = {0};int main(){    next = 1;    memset(&tree[0], 0, sizeof(Trie));    init();    char s1[20], s2[20];    while (scanf("%s %s", s1, s2) == 2) {        Insert(s1), Insert(s2);        int x = Find(s1), y = Find(s2);        unite(x, y);        du[x]++, du[y]++;    }    int temp = seek(Find(s1));    bool ok = true;    for (int i = 1; i < next; i++) {        int s = seek(i);        if (s != i && s != temp) { ok = false; break; }    }    if (ok) {        int cnt = 0;        for (int i = 1; i < next; i++) {            if (du[i] % 2) cnt++;            if (cnt >= 3) break;        }        if (cnt >= 3 || cnt == 1) printf("Impossible\n");        else printf("Possible\n");    }    else printf("Impossible\n");    return 0;}