IsSubsequence.java

package medium;

/**
 * ClassName: IsSubsequence.java
 * Author: chenyiAlone
 * Create Time: 2019/7/29 21:35
 * Description: No.392 Is Subsequence
 * 思路:
 *
 *      贪心
 *
 *
 * 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.
 *
 * Follow up:
 * If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
 *
 * Credits:
 * Special thanks to @pbrother for adding this problem and creating all test cases.
 *
 *
 */
public class IsSubsequence {

    public boolean isSubsequence(String s, String t) {
        int index = 0, slen = s.length(), tlen = t.length();
        if (slen == 0) return true;
        for (int i = 0; i < tlen; i++) {
            if (s.charAt(index) == t.charAt(i)) index++;
            if (index == slen) return true;
        }
        return false;
    }

}