```
public class Solution {
public boolean isInterleave(String s1, String s2, String s3) {
int len1 = s1.length(), len2 = s2.length(), len3 = s3.length();
boolean dp[][][] = new boolean[len1+1][len2+1][len3+1];
dp[len1][len2][len3] = true;
for(int i = len1; i >= 0; i--){
for(int j = len2; j >= 0; j--){
for(int k = len3 - 1; k >= 0; k--){
dp[i][j][k] |= ((i < len1 && s1.charAt(i) == s3.charAt(k) ? dp[i+1][j][k+1] : false) |
(j < len2 && s2.charAt(j) == s3.charAt(k) ? dp[i][j+1][k+1] : false));
}
}
}
return dp[0][0][0];
}
}
```