Leetcode: Interleaving String

class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        if (s1.size() + s2.size() != s3.size()) return false;

        bool dp[s1.size()+1][s2.size()+1];

        for (int len1 = 0 ; len1 <= s1.size() ; len1++) {
            for (int len2 = 0 ; len2 <= s2.size() ; len2++) {
                if (len1 == 0 && len2 == 0) { dp[0][0] = true; continue; }

                dp[len1][len2] = false;
                if (len1 != 0)
                    dp[len1][len2] |= (s1[len1-1] == s3[len1+len2-1] && dp[len1-1][len2]);

                if (len2 != 0)
                    dp[len1][len2] |= (s2[len2-1] == s3[len1+len2-1] && dp[len1][len2-1]);
            }
        }

        return dp[s1.size()][s2.size()];
    }
};