[LeetCode Daily Question] 1625. The smallest lexicographical string after performing an operation (medium)

1625. The lexicographically smallest string after performing an operation

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BFS enumeration

The topic is concise and concise, and the amount of data is not large. Let's search with BFS.

class Solution {
    
    
public:
    string findLexSmallestString(string s, int a, int b) {
    
    
        queue<string> q;
        int n=s.length();
        string res=s;
        q.push(s);
        unordered_set<string> vis;
        vis.insert(s);
        while(!q.empty()){
    
    
            string ss=q.front();
            q.pop();
            res=min(res,ss);
            //累加
            string s1=ss;
            for(int i=1;i<n;i+=2){
    
    
                s1[i]=(s1[i]-'0'+a)%10+'0';
            }
            if(!vis.count(s1)){
    
    
                vis.insert(s1);
                q.push(s1);
            }
            //轮转
            string s2=ss;
            s2=ss.substr(n-b)+ss.substr(0,n-b);
            if(!vis.count(s2)){
    
    
                vis.insert(s2);
                q.push(s2);
            }
        }
        return res;
    }
};