class Solution {    public boolean isInterleave(String s1, String s2, String s3) {        if(s1.length()+s2.length()!=s3.length())            return false;        boolean [][] dp=new boolean[s1.length()+1][s3.length()+1];        dp[0][0]=true;        for(int i=0;i<=s1.length();i++)            for(int j=i;j<=s3.length();j++)            {                if(i>0&&s1.charAt(i-1)==s3.charAt(j-1))                    dp[i][j]=dp[i-1][j-1];                int k=j-i;                if(k<=s2.length()&&k>0&&s2.charAt(k-1)==s3.charAt(j-1))                    dp[i][j]=dp[i][j]||dp[i][j-1];            }        return dp[s1.length()][s3.length()];    }}