题目大意：问s是不是t的子序列。
Problem:
https://leetcode.com/problems/is-subsequence/description/
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.
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?
Solution: Brute force
Time Complexity: O(|s| + |t|)
Space Complexity: O(1)
C++
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// Author: Huahua // Running time: 65 ms (beats 99.37%) class Solution { public: bool isSubsequence(const string& s, const string& t) { int i = 0; const int n = t.length(); for (const char c : s) { while (i < n && t[i] != c) ++i; if (i++ == n) return false; } return true; } }; |
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