LeetCode-in-Java

392. Is Subsequence

Easy

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not).

Example 1:

Input: s = “abc”, t = “ahbgdc”

Output: true

Example 2:

Input: s = “axc”, t = “ahbgdc”

Output: false

Constraints:

• 0 <= s.length <= 100
• 0 <= t.length <= 104
• s and t consist only of lowercase English letters.

Follow up: Suppose there are lots of incoming s, say s1, s2, ..., sk where k >= 109, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?

Solution

public class Solution {
    public boolean isSubsequence(String s, String t) {
        int i = 0;
        int j = 0;
        int n = t.length();
        int m = s.length();
        if (m == 0) {
            return true;
        }
        while (j < n) {
            if (s.charAt(i) == t.charAt(j)) {
                i++;
                if (i == m) {
                    return true;
                }
            }
            j++;
        }
        return false;
    }
}

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