Interleaving String

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        int l1 = s1.length();
        int l2 = s2.length();
        int l3 = s3.length();
        
        if(l3 != (l1+l2))
            return false;
        
        bool dp[l1+1][l2+1];
        for(int i=0;i<l1+1;i++){
            for(int j=0;j<l2+1;j++){
                if(i==0 && j==0){
                    dp[i][j] = true;
                }else if (i == 0){
                    dp[i][j] = (dp[i][j-1] && s2[j-1] == s3[i+j-1]);
                }else if (j == 0){
                    dp[i][j] = (dp[i-1][j] && s1[i-1] == s3[i+j-1]);
                }else {
                    dp[i][j] = (dp[i][j-1] && s2[j-1] == s3[i+j-1]) || (dp[i-1][j] && s1[i-1] == s3[i+j-1]); 
                }
            }
        }
        return dp[l1][l2];
    }
};