【紫书】Play on Words UVA - 10129 欧拉回路

#define _CRT_SECURE_NO_WARNINGS
#include "stdio.h"
#include<stdio.h>
#include<algorithm>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<iostream>
#include<string.h>
#include<queue>
#include<string>
#include<sstream>
#include<stack>
#include<cmath>
using namespace std;
const int maxn = 1e5 + 5;
char s[maxn][1005];
char ss[1005];
int in[256], out[256]; 
//两个点入度不等于出度且一个差+1，一个-1
int f[256];
int find(int x) {
    return f[x] == x ? x : f[x] = find(f[x]);
}
void un(int x, int y) {
    int u = find(x);
    int v = find(y);
    f[u] = v;
}
bool same(int x,int y) {
    return find(x) == find(y);
}
int main() {
    int t; cin >> t; while (t--) {
        int n; cin >> n;
        for (int i = 0; i < 256; i++) f[i] = i;
        memset(in, 0, sizeof(in)); memset(out, 0, sizeof(out));
        for (int i = 0; i < n; i++) {
            scanf("%s", ss);
            int len = strlen(ss);
            out[ss[0]]++; in[ss[len - 1]]++;
            un(ss[0], ss[len - 1]);
            
        }
        int ok = 1; //连通
        int yes = 0;//出入度
        vector<int> temp;
        for (int i = ‘a‘; i <= ‘z‘; i++)if(out[i]+in[i]) {//出现过的字母
            if (!same(‘a‘, i)) { ok = 0; break; }
            if (out[i] != in[i]) {
                temp.push_back(i);
            }
        }
        
        if (temp.size() == 2) {
            int f = temp.front(), b = temp.back();
            if ((abs(in[f] - out[f]) == 1) && (abs(in[b] - out[b]) == 1) && (in[f] + in[b] == out[f] + out[b]))yes=1;
        }
        else if (temp.size() == 0)yes = 1;
        
        if (ok&&yes)cout << "Ordering is possible.\n";
        else cout << "The door cannot be opened.\n";
        
    }
    
    system("pause");
    return 0;
}