LeetCode – Is Subsequence (Java)

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Given a string s and a string t, check if s is subsequence of t.

You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).

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

Java Solution

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

2 thoughts on “LeetCode – Is Subsequence (Java)”

  2. My answer is quite similar to this one. Can someone spot the reason why my code fails?

    public boolean isSubsequence(String s, String t) {
    if (s.length() > t.length())
    return false;

    int i = 0 ;
    int j = 0 ;

    if ( j == s.length())
    return true;

    while (i < t.length())
    if ( t.charAt( i ++ ) == s.charAt(j ))
    if ( j++ == s.length())
    return true;

    return false;
    }

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