16th feb, 2021; favourite problem of the day; problem link: https://www.interviewbit.com/problems/word-ladder-i/

Word_Ladder_I.cpp

bool differByOneChar(string &a, string &b){
    int diff = 0;
    for(int i=0; i<a.size(); ++i){
        if(a[i]!=b[i]) diff++;
        if(diff>1) return false;
    }
    return diff==1;
}
int dfsHelper(unordered_map<string, vector<string>> &adj, string A, string B){
    queue<string> s;
    unordered_map<string, int> vis;
    s.push(A);
    int minDist = 0;
    while(!s.empty()){
        int size = s.size();
        while(size--){
            string temp = s.front(); s.pop();
            vis[temp]=1;
            if(temp==B){
                return minDist+1;
            }
            for(string v:adj[temp]){
                if(vis[v]==0){
                    s.push(v);
                }
            }
        }
        minDist++;
    }
    return 0;
}
int Solution::solve(string A, string B, vector<string> &C) {
    C.push_back(A);
    C.push_back(B);
    unordered_map<string, vector<string>> adj;
    for(int i=0; i<C.size()-1; ++i){
        for(int j=i+1; j<C.size(); ++j){
            bool res = differByOneChar(C[i], C[j]);
            if(res){
                adj[C[i]].push_back(C[j]);
                adj[C[j]].push_back(C[i]);
            }
        }
    }
    return dfsHelper(adj, A, B);
}