LeetCode-Interleaving String（JAVA）

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于 2020-02-10 00:27:14 发布

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分类专栏： LEETCODE 文章标签： leetcode 字符串

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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

说明：字符串s3是否能够由字符串s1和s2组成，s1和s2彼此的字符顺序不变
定义dp[i][j]表示由s1的前i和字符和s2的前j个字符组成s3的前i+j个字符

class Solution {
    public boolean isInterleave(String s1, String s2, String s3) {
        int n1 = s1.length();
        int n2 = s2.length();
        int n3 = s3.length();
        if(n1 + n2 != n3) {
            return false;
        }
        
        boolean[][] dp = new boolean [n1 + 1][n2 + 1];
        dp[0][0] = true;
        
        for(int i = 1; i < n1 + 1; i++) {
            if(s1.charAt(i - 1) != s3.charAt(i - 1)) {
              break;  
            } 
            dp[i][0] = true;
        }
        
        for(int i = 1; i< n2 + 1; i++) {
            if(s2.charAt(i - 1) != s3.charAt(i - 1)) {
                break;
            } 
            dp[0][i]  = true;
        }
        
        for(int i = 1; i < n1 + 1; i++) {
            for(int j = 1; j < n2 + 1; j++) {
                int k = i + j;
                if(s1.charAt(i - 1) == s3.charAt(k - 1)) {
                    dp[i][j] = dp[i - 1][j] ||dp[i][j];
                }
                if(s2.charAt(j - 1) == s3.charAt(k - 1)) {
                    dp[i][j] = dp[i][j - 1] || dp[i][j];
                }
            }
        }
        return dp[n1][n2];
    }
}