Edit distance leetcode

//link: https://leetcode.com/problems/edit-distance/description/

int solve(int i, int j, string s1, string s2,vector<vector<int>>& dp){
 //base case
 if(j<0) return i+1;
 if(i<0) return j+1;

 if(dp[i][j]!=-1) return dp[i][j];
 if(s1[i] == s2[j]){
 return dp[i][j] = solve(i-1,j-1,s1,s2,dp);
 }
 int del = solve(i-1,j,s1,s2,dp);
 int rp = solve(i-1,j-1,s1,s2,dp);
 int ins = solve(i,j-1,s1,s2,dp);
 return dp[i][j] =1+ min({del,rp,ins});
 }
 int minDistance(string word1, string word2) {
 int n = word1.length();
 int m = word2.length();
 vector<vector<int>> dp(n+1,vector<int>(m+1,-1));
 return solve(n-1,m-1,word1,word2,dp);
 }