521. Longest Uncommon Subsequenc

Description

Given a group of two strings, you need to find the longest uncommon subsequence of this group of two strings. The longest uncommon subsequence is defined as the longest subsequence of one of these strings and this subsequence should not be anysubsequence of the other strings.

A subsequence is a sequence that can be derived from one sequence by deleting some characters without changing the order of the remaining elements. Trivially, any string is a subsequence of itself and an empty string is a subsequence of any string.

The input will be two strings, and the output needs to be the length of the longest uncommon subsequence. If the longest uncommon subsequence doesn't exist, return -1.

Example 1:

Input: "aba", "cdc"
Output: 3
Explanation: The longest uncommon subsequence is "aba" (or "cdc"),
because "aba" is a subsequence of "aba",
but not a subsequence of any other strings in the group of two strings.

Note:

1. Both strings' lengths will not exceed 100.
2. Only letters from a ~ z will appear in input strings.

Solution

Compare string, O(min(m, n)), S(1)

一开始看这道题有点蒙，后来马上发现，这不就是比较两个字符串是否equal吗。。

class Solution {
    public int findLUSlength(String a, String b) {
        if (a == null || b == null) {
            return -1;
        }
        
        if (a.equals(b)) {  // O(min(m, n))
            return -1;
        }
        
        return Math.max(a.length(), b.length());
    }
}