392. Is Subsequence

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392. Is Subsequence

Description

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:

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Input: s = "abc", t = "ahbgdc"
Output: true

Example 2:

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Input: s = "axc", t = "ahbgdc"
Output: false

Constraints:

  • 0 <= s.length <= 100
  • 0 <= t.length <= 10^4
  • s and t consist only of lowercase English letters.

Follow up: Suppose there are lots of incoming s, say s<sub>1</sub>, s<sub>2</sub>, ..., s<sub>k</sub> where k >= 10^9, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    bool isSubsequence(string s, string t) {
        int idx1 = 0, idx2 = 0;
        while (idx1 < s.size() && idx2 < t.size()) {
            if (s[idx1] == t[idx2]) {
                idx1++;
            }
            idx2++;
        }
        return idx1 == s.size();
    }
};