UVA 10129 欧拉回路

代码

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/*
 * @Author: Axiuxiu
 * @Date: 2021-11-03 15:24:40
 * @LastEditors: Axiuxiu
 * @LastEditTime: 2021-11-03 16:20:00
 * @Description: 单词问题
 */

#include <stdio.h>
#include <string.h>

#define MAXN 1005

int G[26][26];    // 图矩阵
int vis[26][26];  // 访问矩阵， 矩阵内数值等于有向边条数

int get_letter_id(char ch)
{
    return ch - 'a';
}

bool dfs(int u)
{
    bool end = true;
    for (int v = 0; v < 26; v++) {
        if (vis[u][v]) {
            end = false;
            vis[u][v] -= 1;
            if (dfs(v))
                return true;
        }
    }
    if (end) {
        // 到达终点检查是否遍历所有边
        for (int i = 0; i < 26; i++) {
            for (int j = 0; j < 26; j++) {
                if (vis[i][j])
                    return false;
            }
        }
        return true;
    }
    else {
        return false;
    }
}

int main()
{
    int  n;
    char word[MAXN];

    while (scanf("%d", &n) == 1) {
        memset(G, 0, sizeof(G));

        // 读取n个单词
        for (int i = 0; i < n; i++) {
            scanf("%s", word);
            int u   = get_letter_id(word[0]);
            int len = strlen(word);
            int v   = get_letter_id(word[len - 1]);
            G[u][v] += 1;
        }

        // 深度优先遍历
        bool flag = false;
        for (int u = 0; u < 26; u++) {
            // 初始化访问数组
            memcpy(vis, G, sizeof(G));
            if (dfs(u)) {
                puts("Ordering is possible.");
                flag = true;
                break;
            }
        }
        if (!flag) {
            puts("The door cannot be opened.");
        }
    }
}