面试经典150题——Day26

一、题目

392. Is Subsequence

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., “ace” is a subsequence of “abcde” while “aec” is not).

Example 1:

Input: s = “abc”, t = “ahbgdc”
Output: true
Example 2:

Input: s = “axc”, t = “ahbgdc”
Output: false

Constraints:

0 <= s.length <= 100
0 <= t.length <= 104
s and t consist only of lowercase English letters.

Follow up: Suppose there are lots of incoming s, say s1, s2, …, sk where k >= 109, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?

题目来源： leetcode

二、题解

class Solution {
public:
    bool isSubsequence(string s, string t) {
        int n1 = s.length();
        int n2 = t.length();
        if(n1 > n2) return false;
        int index = 0;
        for(int i = 0;i < n2;i++){
            if(s[index] == t[i]) index++;
        }
        return index == n1;
    }
};