Codeforces Round #288 (Div. 2) D. Tanya and Password 欧拉通路
2016-06-30 23:36
435 查看
题目链接:
题目
D. Tanya and Passwordtime limit per test 2 seconds
memory limit per test 256 megabytes
inputstandard input
outputstandard output
问题描述
While dad was at work, a little girl Tanya decided to play with dad's password to his secret database. Dad's password is a string consisting of n + 2 characters. She has written all the possible n three-letter continuous substrings of the password on pieces of paper, one for each piece of paper, and threw the password out. Each three-letter substring was written the number of times it occurred in the password. Thus, Tanya ended up with n pieces of paper.Then Tanya realized that dad will be upset to learn about her game and decided to restore the password or at least any string corresponding to the final set of three-letter strings. You have to help her in this difficult task. We know that dad's password consisted of lowercase and uppercase letters of the Latin alphabet and digits. Uppercase and lowercase letters of the Latin alphabet are considered distinct.
输入
The first line contains integer n (1 ≤ n ≤ 2·105), the number of three-letter substrings Tanya got.Next n lines contain three letters each, forming the substring of dad's password. Each character in the input is a lowercase or uppercase Latin letter or a digit.
输出
If Tanya made a mistake somewhere during the game and the strings that correspond to the given set of substrings don't exist, print "NO".If it is possible to restore the string that corresponds to given set of substrings, print "YES", and then print any suitable password option.
样例
input5
aca
aba
aba
cab
bac
output
YES
abacaba
题意
给你n个串每个串三个字母,问你存不存在一个长度为n+2的串,使得上面输入的串刚好是这个串的所有的长度为第三的子串。题解
对于输入xyz,xy建一个节点,yz建一个节点,然后xy连一条边到yz,跑欧拉通路。代码
#include<iostream> #include<cstring> #include<cstdio> #include<algorithm> #include<vector> #include<string> using namespace std; const int maxn = 10101; int n; vector<int> G[maxn]; int in[maxn], out[maxn]; int mp[256]; string ans; int cnt[maxn]; char rmp[111]; void init() { for (int i = 'a'; i <= 'z'; i++) { mp[i] = i - 'a'; rmp[i - 'a'] = i; } for (int i = 'A'; i <= 'Z'; i++) { mp[i] = i - 'A' + 26; rmp[i - 'A' + 26] = i; } for (int i = '0'; i <= '9'; i++) { mp[i] = i - '0' + 52; rmp[i - '0' + 52] = i; } memset(in, 0, sizeof(in)); memset(out, 0, sizeof(out)); memset(cnt, 0, sizeof(cnt)); } //有向图欧拉通路 void dfs(int u) { while (cnt[u] < G[u].size()) dfs(G[u][cnt[u]++]); ans += rmp[u % 62]; } int main() { init(); scanf("%d", &n); char str[22]; for (int i = 0; i < n; i++) { scanf("%s", str); int u = mp[str[0]] * 62 + mp[str[1]]; int v = mp[str[1]] * 62 + mp[str[2]]; G[u].push_back(v); in[v]++, out[u]++; } int st=-1,ed=-1,tmp=0; int su = 1,cnt=0; for (int i = 0; i < maxn; i++) { if (abs(in[i] - out[i]) >= 2) { su = 0; break; } if (in[i] - out[i] == 1) { if (ed != -1) { su = 0; break; } ed = i; } else if (in[i] - out[i] == -1) { if (st != -1) { su = 0; break; } st = i; } if (in[i] != out[i]) cnt++; if (in[i] == out[i] && in[i]>0) tmp = i; } if (cnt == 0) { st = tmp; } if (su) { dfs(st); ans.push_back(rmp[st/62]); if (ans.length() == n + 2) { reverse(ans.begin(), ans.end()); cout << "YES" << endl; cout << ans << endl; } else { cout << "NO" << endl; } } else cout << "NO" << endl; return 0; }
相关文章推荐
- Lightoj 1025 - The Specials Menu
- 《剑指offer》-二进制中1的个数
- iOS面试题一
- 关于unity中BindChannels的理解
- 高德地图 获取sha1
- 初识Postman
- 不是经常用到的回调方法
- 指向对象的指针
- iOS GPUImage之GPUImageVideoCamera(3)
- 机器学习实践之手写数字识别- 数据阶段分析总结
- MAC 安装mysql 5.7 以上问题解决,MAC安装brew所遇问题解决
- LeetCode OJ combine 3
- 指向对象的指针
- Spark Streaming(上)--实时流计算Spark Streaming原理介绍
- http-客户端识别与cookie机制
- C#基础
- FFmpeg解码H264及swscale缩放详解
- 《终无言》感
- 数组和字符串中的开灯问题
- 简单主页搭建