[LeetCode] 392. Is Subsequence

题目描述

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.

分析

这里只需要对两个字符串分别进行一次遍历，对长的字符串进行遍历，用一个变量计算当前应该查看的子字符串的位置，然后看长的字符串的当前位置的字母是否和子字符串的位置的字母相等，如果相等则两个字符串的位置都加1，否则只有长的字符串的位置加1，最后看是否访问完了子字符串的最后一个字母即可。

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