Is One String a Subsequence of Another

easy string two pointers

Problem

Given two strings s and t, decide whether every character of s appears in t in the same order (not necessarily contiguous). Walk both strings together; advance the s pointer only when the current characters match.

Inputs = "ace", t = "abcde"

Outputtrue

a, c, e appear at indices 0, 2, 4 in t.

def is_subsequence(s, t):
    i = 0
    for ch in t:
        if i < len(s) and ch == s[i]:
            i += 1
    return i == len(s)

function isSubsequence(s, t) {
  let i = 0;
  for (let j = 0; j < t.length && i < s.length; j++) {
    if (t[j] === s[i]) i++;
  }
  return i === s.length;
}

class Solution {
    public boolean isSubsequence(String s, String t) {
        int i = 0;
        for (int j = 0; j < t.length() && i < s.length(); j++) {
            if (t.charAt(j) == s.charAt(i)) i++;
        }
        return i == s.length();
    }
}

bool isSubsequence(string s, string t) {
    int i = 0;
    for (int j = 0; j < (int)t.size() && i < (int)s.size(); j++) {
        if (t[j] == s[i]) i++;
    }
    return i == (int)s.size();
}

Time: O(|t|) Space: O(1)