动态规划-392. Is Subsequence

题目：

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 sis 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.

题意解析：给定一个字符串s和一个字符串t.检查字符串s是否是字符串t的子序列。子序列的定义是由原序列删除一些字符但不打乱原序列的顺序所得到的

//不需要DP,class Solution {    public boolean isSubsequence(String s, String t) {        int indexS = 0;        int indexT = 0;        if(s.length() == 0) return true;        //遍历串T        while(indexT < t.length()){            //如果串s存在和串t相同的字符，则增加indexS，可以想象当前字符已经检查通过，进入下一个字符检查            if(s.charAt(indexS) == t.charAt(indexT++)){                indexS++;                //如果indexS的长度和s的长度相同，则返回true                if(indexS == s.length()) return true;            }                                    }        return false;    }}