[Leetcode] #392 Is Subsequence

Discription:

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).

Example 1:
s = "abc", t = "ahbgdc"

Return true.

Example 2:
s = "axc", t = "ahbgdc"

Return false.

Solution:

bool isSubsequence(string s, string t) {
	if (s.size()>t.size()) return false;
	int len1 = s.size(), len2 = t.size(), k1 = 0, k2 = 0;
	while (k1 < len1 && k2 < len2)
	{
		if (s[k1] == t[k2]) k1++;
		k2++;
	}
	return k1 == len1;
}

bool isSubsequence(string s, string t) {  //DP
	int rows = s.size(), cols = t.size();
	vector<vector<bool>> dp(rows + 1, vector<bool>(cols + 1, false));
	for (int i = 0; i <= cols; i++){
		dp[0][i] = true;
	}
	for (int i = 1; i <= rows; i++){
		for (int j = 1; j <= cols; j++){
			if (s[i-1] == t[j-1])
				dp[i][j] = dp[i - 1][j - 1];
			else
				dp[i][j] = dp[i][j - 1];
		}
	}
	return dp[rows][cols];
}

GitHub-Leetcode: https://github.com/wenwu313/LeetCode