Add to List 392. Is Subsequence

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.

解答：
从s和t的首端开始遍历比较字符是否相等，如果不等，则增加在t中的下标位置；
如果相等，则同时增加在s和t中的下标位置。
如果t中的指标位置增长到了t的末尾，而s中的指标还没有增长的末尾，则返回false。如果s中的指标先增长到了末尾，则返回true。

C语言：

bool isSubsequence(char* s, char* t) {    while(*t) {        s += (*s == *t++);    }       return !*s;}

C++：

class Solution {public:    bool isSubsequence(string s, string t) {        if(s == "" && t == "") return true;        for(int i = 0, j = 0; j < t.size(); j++) {            if(t[j] == s[i]) i++;            if(i == s.size()) return true;        }        return false;    }};