CF 518A(Vitaly and Strings-構造)

CF 518A(Vitaly and Strings-構造)

Vitaly is a diligent student who never missed a lesson in his five years of studying in the university. He always does his homework on time and passes his exams in time.

During the last lesson the teacher has provided two strings s and t to Vitaly. The strings have the same length, they consist of lowercase English letters, string s is lexicographically smaller than string t. Vitaly wondered if there is such string that is lexicographically larger than string s and at the same is lexicographically smaller than string t. This string should also consist of lowercase English letters and have the length equal to the lengths of strings s and t.

Let's help Vitaly solve this easy problem!

The first line contains string s (1?≤?|s|?≤?100), consisting of lowercase English letters. Here, |s| denotes the length of the string.

The second line contains string t (|t|?=?|s|), consisting of lowercase English letters.

It is guaranteed that the lengths of strings s and t are the same and string s is lexicographically less than string t.

If the string that meets the given requirements doesn't exist, print a single string "No such string" (without the quotes).

If such string exists, print it. If there are multiple valid strings, you may print any of them.

a
c

b

aaa
zzz

kkk

abcdefg
abcdefh

No such string

String s?=?s1s2... sn is said to be lexicographically smaller than t?=?t1t2... tn, if there exists such i, that s1?=?t1,?s2?=?t2,?... si?-?1?=?ti?-?1,?si?ti.

#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
#define For(i,n) for(int i=1;i<=n;i++)
#define Fork(i,k,n) for(int i=k;i<=n;i++)
#define Rep(i,n) for(int i=0;i=0;i--)
#define Forp(x) for(int p=pre[x];p;p=next[p])
#define Forpiter(x) for(int &p=iter[x];p;p=next[p])  
#define Lson (x<<1)
#define Rson ((x<<1)+1)
#define MEM(a) memset(a,0,sizeof(a));
#define MEMI(a) memset(a,127,sizeof(a));
#define MEMi(a) memset(a,128,sizeof(a));
#define INF (2139062143)
#define F (100000007)
#define MAXN (100+10)
long long mul(long long a,long long b){return (a*b)%F;}
long long add(long long a,long long b){return (a+b)%F;}
long long sub(long long a,long long b){return (a-b+(a-b)/F*F+F)%F;}
typedef long long ll;
char s[MAXN],t[MAXN];
int main()
{
//	freopen("a.in","r",stdin);
//	freopen(".out","w",stdout);
	scanf("%s%s",s,t);
	
	int n=strlen(s);
	
	s[n-1]++;
	RepD(i,n-1)
	{
		if (s[i]>'z')
		{
			s[i]='a';
			if (i>0) s[i-1]++;
			else
			{
				cout<<"No such string\n";
				return 0;
			}
		} 
	} 
	
	bool flag=0;
	Rep(i,n)
	{
		if (s[i]==t[i]) continue;
		else if (s[i]