Question
Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.
Example 1:
Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"
Output: true
Example 2:
Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbbaccc"
Output: false
Solution
Dynamic Programming
Code
class Solution {
public boolean isInterleave(String s1, String s2, String s3) {
if(s1.length() + s2.length() != s3.length()) return false;
boolean[][] cache = new boolean[s1.length()+1][s2.length()+1];
cache[0][0] = true;
for(int i=1; i<=s1.length(); i++)
cache[i][0] = cache[i-1][0] && s3.charAt(i-1) == s1.charAt(i-1);
for(int j=1; j<=s2.length(); j++)
cache[0][j] = cache[0][j-1] && s3.charAt(j-1) == s2.charAt(j-1);
for(int i=1; i<=s1.length(); i++) {
for(int j=1; j<=s2.length(); j++) {
cache[i][j] = (cache[i-1][j] && s3.charAt(i+j-1) == s1.charAt(i-1)) ||
(cache[i][j-1] && s3.charAt(i+j-1) == s2.charAt(j-1));
}
}
return cache[s1.length()][s2.length()];
}
}
Performance
O(s1.length*s2.length)