[LeetCode]97. Interleaving String

https://leetcode.com/problems/interleaving-string/

判断s3是否是s1 & s2交互形成的

首先判断长度不合适直接返回。多开一位数组，初始化数组左侧和上侧。然后dp[i][j]为true仅有两种情况：dp[i - 1][j] 同时s1[i] == s3[i + j - 1]；或者，dp[i][j - 1] 同时s2[j] == s3[i + j - 1]

public 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][s2.length() + 1];
dp[0][0] = true;
for (int i = 1; i < dp.length; i++) {
dp[i][0] = (dp[i - 1][0] && s1.charAt(i - 1) == s3.charAt(i - 1));
}
for (int i = 1; i < dp[0].length; i++) {
dp[0][i] = (dp[0][i - 1] && s2.charAt(i - 1) == s3.charAt(i - 1));
}
for (int i = 1; i < dp.length; i++) {
for (int j = 1; j < dp[0].length; j++) {
dp[i][j] = ((dp[i - 1][j] && s1.charAt(i - 1) == s3.charAt(i + j - 1)) || (dp[i][j - 1] && s2.charAt(j - 1) == s3.charAt(i + j - 1)));
}
}
return dp[s1.length()][s2.length()];
}
}