392. Is Subsequence LeetCode

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.

题目解析：改题目就是要求在给定的字符串中找到其“子字符串”，这里的子字符串并不是传统的形式，而是只在乎顺序而不在乎其字符串中字符的连贯。这就比较简单了，只需要一一检查子字符串在给定字符串中是否存在即可。

代码：

class Solution {public:    bool isSubsequence(string s, string t) {        int m=t.size();        int k=0;              //用于遍历字符串s        for(int i=0;i<m;i++)  //循环检查给定字符串        {            if(s[k]==t[i])            {                k++;            }        }        if(k==s.size()) return true;//判断子字符串是否正确存在与给定字符串的条件        else return false;    }};