392. Is Subsequence Medium

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.

思路：判断条件是s中字符都在t中并且顺序和在t中顺序一样。直接循环查找，用count记录s中有多少顺序相同字符在t中，count = s.size()返回true。

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