POJ_2513Colored Sticks 字典树+

比较考察技术含量的一道题。

参考链接:http://blog.csdn.net/lyy289065406/article/details/6647445

题目链接:http://poj.org/problem?id=2513

首先差不多能想到这事欧拉路，然后发现没法构图。没有尝试使用map，刚好最近在学字典树就直接上了。

然后就是并查集判断图连通。

参考链接里面的：连通图判断（并查集）+字典树（映射字符串）+欧拉路（奇数节点0个或2个）

注意：最后需要销毁字典树所创建的节点，不然会RE！

代码：先字典树，然后并查集，然后直接主函数中判断欧拉路

#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
using namespace std;
#define maxm 500055
#define maxn 500055
#define maxnode 30

struct trie {
    trie * next[maxnode];
    int id;
};
trie *root;
int totid = 1;
trie * newnode() {
    trie * t;
    t = (trie*)malloc(sizeof(trie));
    t->id = 0;
    for (int i = 0; i < maxnode; i++)
        t->next[i] = 0;
    return t;
}
void init() {
    root = (trie *)malloc(sizeof(trie));
    root->id = 0;
    for (int i = 0; i < maxnode; i++)
        root->next[i] = 0;
}
int insert_find_Str(char s[]) {
    trie *p = root, *q;
    int len = strlen(s), i = 0;
    while (i < len && p->next[s[i] - 'a']) {
        p = p->next[s[i] - 'a'];
        i++;
    }
    if (i == len && p->id) return p->id;
    else if (i == len) return p->id = totid++;
    while (i < len) {
        q = newnode();
        p->next[s[i] - 'a'] = q;
        p = p->next[s[i] - 'a'];
        i++;
    }
    p->id = totid++;
    return p->id;
}
void deltrie(trie* node) {
    while (node) {
        for (int i = 0; i < 26; i++) {
            if ((node->next)[i])
                deltrie((node->next)[i]);
        }
        free(node);
        node = 0;
    }
}

int f[maxn];
int deg[maxn];
char st[maxn], anost[maxn];

void init_ds(int n) {
    for (int i = 1; i < n - 1; i++)
        f[i] = i;
}
int find(int x) {
    if (x == f[x])
        return f[x];
    return f[x] = find(f[x]);
}
void unite(int x, int y) {
    int fx = find(x);
    int fy = find(y);
    if (fx == fy) return;
    f[fx] = fy;
}

int main() {
    init();
    init_ds(maxn);
    memset(deg, 0, sizeof deg);
    while (scanf("%s", st) > 0) {
        scanf("%s", anost);
        int a = insert_find_Str(st);
        int b = insert_find_Str(anost);
        deg[a]++; deg[b]++;
        unite(a, b);
    }
    if (totid == 1) {
        printf("Possible
");
        return 0;
    }
    bool flag = true;
    for (int i = 2; i < totid; i++) {
        if (find(i) != find(i - 1)) {
            flag = false;
            break;
        }
    }
    if (!flag) {
        printf("Impossible
");
    }
    else {
        int oddnum = 0;
        for (int i = 1; i < totid; i++)
            if (deg[i] & 1) oddnum++;
        if (oddnum == 0 || oddnum == 2) {
            printf("Possible
");
        }
        else
            printf("Impossible
");
    }
    deltrie(root);
}

题目：

Colored Sticks

Time Limit: 5000MS		Memory Limit: 128000K
Total Submissions: 37263		Accepted: 9775

Description

You are given a bunch of wooden sticks. Each endpoint of each stick is colored with some color. Is it possible to align the sticks in a straight line such that the colors of the endpoints that touch are of the same color?

Input

Input is a sequence of lines, each line contains two words, separated by spaces, giving the colors of the endpoints of one stick. A word is a sequence of lowercase letters no longer than 10 characters. There is no more than 250000 sticks.

Output

If the sticks can be aligned in the desired way, output a single line saying Possible, otherwise output Impossible.

Sample Input

blue red
red violet
cyan blue
blue magenta
magenta cyan

Sample Output

Possible

Hint

Huge input,scanf is recommended.