Codeforces Round #265 (Div. 2) 题解

// File Name: c.cpp
// Author: darkdream
// Created Time: 2014年09月07日 星期日 23时55分52秒

#include<vector>
#include<list>
#include<map>
#include<set>
#include<deque>
#include<stack>
#include<bitset>
#include<algorithm>
#include<functional>
#include<numeric>
#include<utility>
#include<sstream>
#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<ctime>
#define LL long long

using namespace std;
int a[1005];
int b[1005];
char str[1005];
int main(){
int n , p ;
scanf("%d %d",&n,&p);
scanf("%s",&str[1]);
memset(a,0,sizeof(a));
memset(b,0,sizeof(b));
for(int i = 1;i <= n;i ++)
{
a[i] =  str[i] - 'a' + 1;
}
int ans = 0 ;
//for(int i =1 ;i <= n;i++)
//  printf("%d ",a[i]);
for(int i = n;i >= 1 ;i --)
{
int j ;
int s;
for(s = a[i] + 1 ; s <= p ;s ++)
{
if(s != a[i-1] &&( i-2 == -1 || (s != a[i-2]) ))
{
b[i] = s;
b[i-1] = a[i-1];
break;
}
}
if(s == p + 1)
continue;
//printf("\n%d %d\n",i,s);
for( j = i+1;j<= n;j ++)
{
for( s = 1; s <= p;s ++)
{
if(s != b[j-1] && s!= b[j-2])
{
b[j] = s;
//printf("%d***\n",s);
break;
}
}
if(s == p + 1)
{
break;
}
}
if(j == n+1)
{
ans = i;
break;
}
}
if(!ans)
{
printf("NO\n");
return 0 ;
}
for(int i = 1;i <= ans -1;i ++)
printf("%c",a[i] + 'a' -1 );
for(int j = ans ;j <= n;j ++)
printf("%c",b[j] + 'a' -1);

return 0;
}