dp with dimensions (len(s1)+1) x (len(s2)+1).dp[0][0] to true as an empty string is an interleaving of two empty strings.dp based on whether previous characters of s1 or s2 match with s3.dp table starting from dp[1][1].dp[i][j], set it to true if either dp[i-1][j] is true and s1[i-1] matches s3[i+j-1], or dp[i][j-1] is true and s2[j-1] matches s3[i+j-1].dp[len(s1)][len(s2)].