Huawei interview question: no palindrome string

subject

【 No palindrome string 】
Definition of palindrome string ： Read and reverse the same string
There is already a string that does not contain a palindrome string , The characters of the string are in front of the English letter N individual , And the string does not contain any length greater than or equal to 2 The palindrome of ; Please find the next dictionary order that does not contain palindromes 、 Characters are in front of English letters N individual 、 String with the same length . If it doesn't exist , Please export NO.

Input description ：
The first line has an integer :N（1<=N<=26）, Indicates that each character range of the string is before N English letters of .
Enter a string in the second line （ Input length <=10000）, The input ensures that this string is legal and does not contain a palindrome string .

Output description ：
Output the next dictionary order without palindrome string 、 Characters are in front of English letters N individual 、 String with the same length ; If it doesn't exist , Please export ”NO”.

Example 1：
Input ：

3
cba

Output ：

NO

Example 2：
Input ：

4
dbad

Output ：

dbcd

Code

#include<iostream>
using namespace std;
int main(){
    
    int n;
    cin >> n;
    string str;
    cin >> str;
    int len = str.size();
    if(len == 1) {
    
        cout << "NO" << endl;
        return 0;
    }
    for(int i = len - 1; i >= 0; --i){
    
        char next = str[i] + 1;
        while(next < 'a'+ n){
    
            int flag = 0;
            for(int j = i - 2; j <= i + 2; ++j){
    
                if(j < 0) continue;
                if(j >= len) continue;
                if(j == i) continue;
                if(str[j] == next){
    
                    flag = 1;
                    break;
                }
            }
            if(flag){
    
                next = next + 1;
            }else{
    
                str[i] = next;
                cout << str << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}