2015 暑假多校训练---CRB and String（简单但有很多需要注意地方）

题目链接
http://acm.hust.edu.cn/vjudge/contest/131172#problem/B

Description
CRB has two strings s and t .
In each step, CRB can select arbitrary character c of s and insert any character d ( d ≠ c ) just after it.
CRB wants to convert s to t . But is it possible?

Input
There are multiple test cases. The first line of input contains an integer T , indicating the number of test cases. For each test case there are two strings s and t , one per line.
1 ≤ T ≤ 105
1 ≤ |s| ≤ |t| ≤ 105
All strings consist only of lowercase English letters.
The size of each input file will be less than 5MB.

Output
For each test case, output “Yes” if CRB can convert s to t, otherwise output “No”.

Sample Input
4
a
b
cat
cats
do
do
apple
aapple

Sample Output
No
Yes
Yes
No

题意：输入两个串s，t 问是否能将s串变到t串，操作规则是对s串中的任意一个字符x，可以在其后面添加除x外的任意字符；

思路：对t串从头开始遍历，令k=0，表示当前s串遍历到的位置，若t[i]==s[k], i++;k++; 若不想等则i++，k不变（就是在s[k-1]后添一个字符，注意判断是否添加成功，因为可能前面全是同一个字符且t[i-1]==t[i]，添加不成功时，即不能由s->t） 最后注意判断一下k==|s|
还有要注意特判s[0] t[0] ,因为s串前不可能添加字符；

代码如下：

#include 
#include 
#include 
#include 
#include 
#define eps 1e-8
#define maxn 105
#define inf 0x3f3f3f3f3f3f3f3f
#define IN freopen("in.txt","r",stdin);
using namespace std;
char s[100005],t[100005];

int main()
{
    int T;
    cin>>T;
    while(T--)
    {
        scanf("%s%s",s,t);
        int len1=strlen(s);
        int len2=strlen(t);
        if(s[0]!=t[0])  {puts("No");continue;}
        int k=1;
        int flag=1;
        int f=0;
        for(int i=1;iif(s[k]==t[i]) {
                if(t[i]!=t[0])
                f=1;
                k++; continue;
            }
            else if(t[i]==t[i-1]&&f==0) {flag=0; break;}
            else f=1;
        }
        if(flag&&k==len1) puts("Yes");
        else     puts("No");
    }
    return 0;
}