Today I have done leetcode's September LeetCoding Challenge with cpp.

September LeetCoding Challenge 22

Description

Is Subsequence

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

class Solution {
public:
  bool isSubsequence(string s, string t) {
    int sLen = s.length();
    int tLen = t.length();
    if(sLen > tLen) return false;
    int sPos = 0;
    int tPos = 0;
    while(sPos < sLen && tPos < tLen) {
      if(s[sPos] == t[tPos]) {
        sPos += 1;
      }
      tPos += 1;
    }
    return sPos == sLen;
  }
};

// Accepted
// 19/19 cases passed (3 ms)
// Your runtime beats 49.1 % of cpp submissions
// Your memory usage beats 12.75 % of cpp submissions (6.7 MB)