题：https://leetcode.com/problems/is-subsequence/description/
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 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?
题目大意
字符串 s 是否是 t 的子序列。
思路
贪心算法
按顺序从s中取出一个元素c，从左往右找 t 中出现的 相同元素，若未找到返回false。继续从s中抽取下一个元素，从左往右找 t 中出现的 相同元素且本次起点为上次 t中所找元素的后一位。
class Solution {
public boolean isSubsequence(String s, String t) {
for(int i = 0,j =0 ; i < s.length();i++){
while(j<t.length()){
if(t.charAt(j) == s.charAt(i))
break;
j++;
}
if(j == t.length())
return false;
j++;
}
return true;
}
}