Uva10340

All in All UVA - 10340

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. Input is terminated by EOF.
Output
For each test case output, if s is a subsequence of t.
Sample Input
sequence subsequence person compression VERDI vivaVittorioEmanueleReDiItalia caseDoesMatter CaseDoesMatter
Sample Output
Yes No Yes No

#include<bits/stdc++.h>
#define maxn 100010
using namespace std;
char a[maxn],b[maxn];
int main()
{
    while(scanf("%s %s",a,b)!=EOF)
    {
        int len=strlen(a);
        int len2=strlen(b);
        int i=0,j=0;
            while(j<len2)
            {
                if(i==len)break;
                if(b[j]==a[i])i++,j++;
                else j++;
            }
        if(i==len)printf("Yes\n");
        else printf("No\n");
    }
    return 0;
}

注意点：

i==len;的时候跳出循环，而不是len-1，只有当i==len时才是保证了前面[0,len-1]都存在匹配的字符。