poj 2513 Colored Sticks(欧拉通路+并查集+字典树)

题目链接：poj 2513 Colored Sticks

题目大意：有N个木棍，每根木棍两端被涂上颜色，现在给定每个木棍两端的颜色，不同木棍之间拼接需要颜色相同的

端才可以，问最后能否将N个木棍拼接在一起。

解题思路：欧拉通路+并查集+字典树。欧拉通路，每个节点的统计度，度为奇数的点不能超过2个。并查集，判断节点

是否完全联通。字典树，映射颜色。

#include <cstdio>#include <cstring>#include <string>#include <vector>#include <iostream>#include <algorithm>using namespace std;const int maxn = 5000005;const int sigma_size = 26;typedef pair<int,int> pii;int N, E, far[maxn], cnt[maxn];pii ed[maxn];struct Tire {    int sz, g[maxn][sigma_size];    int val[maxn];    void init();    int idx(char ch);    int insert(char* s);}T;inline int getfar(int x) {    return x == far[x] ? x : far[x] = getfar(far[x]);}bool judge() {    int ret = 0;    for (int i = 1; i <= N; i++) {        if (cnt[i]&1)            ret++;    }    if (ret > 2)        return false;    for (int i = 0; i < E; i++) {        int p = getfar(ed[i].first);        int q = getfar(ed[i].second);        if (p != q) {            N--;            far[p] = q;        }    }    return N <= 1;}int main () {    T.init();    N = E = 0;    char a[11], b[11];    while (scanf("%s%s", a, b) == 2) {        int p = T.insert(a);        int q = T.insert(b);        cnt[p]++, cnt[q]++;        ed[E].first = p;        ed[E].second = q;        E++;    }    printf("%s\n", judge() ? "Possible" : "Impossible");    return 0;}void Tire::init() {    sz = 1;    val[0] = 0;    memset(g[0], 0, sizeof(g[0]));}int Tire::idx(char ch) {    return ch - 'a';}int Tire::insert(char* s) {    int u = 0, n = strlen(s);    for (int i = 0; i < n; i++) {        int v = idx(s[i]);        if (g[u][v] == 0) {            g[u][v] = sz;            memset(g[sz], 0, sizeof(g[sz]));            val[sz++] = 0;        }        u = g[u][v];    }    if (val[u] == 0) {        val[u] = ++N;        far[N] = N;        cnt[N] = 0;    }    return val[u];}