Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.

For example,
Given:
s1 = "aabcc",
s2 = "dbbca",

When s3 = "aadbbcbcac", return true.
When s3 = "aadbbbaccc", return false.

答案

public class Solution {
    boolean check[][];
    String s1;
    String s2;
    String s3;
    public boolean isInterleave(int m,int n)
    {
        if(check[m][n])
        {
            return false;
        }
        check[m][n]=true;
        if(m==s1.length())
        {
            for(;n<s2.length();n++)
            {
                if(s2.charAt(n)!=s3.charAt(m+n))
                {
                    break;
                }
            }
            return n==s2.length();
        }
        if(n==s2.length())
        {
            for(;m<s1.length();m++)
            {
                if(s1.charAt(m)!=s3.charAt(m+n))
                {
                    break;
                }
            }
            return m==s1.length();
        }
        if(s1.charAt(m)==s3.charAt(m+n))
        {
            if(isInterleave(m+1,n))
            {
                return true;
            }
        }
        if(s2.charAt(n)==s3.charAt(m+n))
        {
            if(isInterleave(m,n+1))
            {
                return true;
            }
        }
        return false;
    }
    public boolean isInterleave(String s1, String s2, String s3) {
        if(s1==null||s2==null||s3==null||s1.length()+s2.length()!=s3.length())
        {
            return false;
        }
        int m=s1.length()+1;
        int n=s2.length()+1;
        check=new boolean[m][n];
        this.s1=s1;
        this.s2=s2;
        this.s3=s3;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                check[i][j]=false;
            }
        }
        return isInterleave(0,0);
    }
}