All in All

http://acm.pku.edu.cn/JudgeOnline/problem?id=1936

Description

You have devised a new encryption technique which encodes a message by inserting between its characters randomly generated strings in a clever way. Because of pending patent issues we will not discuss in detail how the strings are generated and inserted into the original message. To validate your method, however, it is necessary to write a program that checks if the message is really encoded in the final string.

Given two strings s and t, you have to decide whether s is a subsequence of t, i.e. if you can remove characters from t such that the concatenation of the remaining characters is s.

Input

The input contains several testcases. Each is specified by two strings s, t of alphanumeric ASCII characters separated by whitespace.The length of s and t will no more than 100000.

Output

For each test case output "Yes", if s is a subsequence of t,otherwise output "No".

Source

Ulm Local 2002

Solving

두 개의 문자열 a와 b가 주어졌을 때 a가 b의 subsequence 인지를 구하는 문제이다.
여기에서 subsequence와 substring의 차이점은 명확하게 알고 넘어가자.
관련 문제로 longest common subsequence문제와 longest common substring문제도 알아두면 좋겠다.

#include <cstdio> #include <cstring> #define MAX_LEN 100000 bool IsSubSequence(char* s, char* t); int main() { char s[MAX_LEN]; char t[MAX_LEN]; while (scanf("%s%s", s, t) == 2) { if (IsSubSequence(s, t)) printf("Yes\n"); else printf("No\n"); } return 0; } bool IsSubSequence(char* s, char* t) { int a = 0; int b = 0; int tlen = strlen(t); while (s[a]) { if (b >= tlen) return false; if (s[a] == t[b++]) a++; } return true; }