LeetCode 392. Is Subsequence 题解（C++）

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该博客介绍了如何用C++解决LeetCode 392题，即判断一个字符串是否为另一个长字符串的子序列。通过设置两个指针，遍历长字符串并比较字符来确定子序列关系。示例包括正确和错误的情况，并提供了思路和具体代码实现。

LeetCode 392. Is Subsequence 题解（C++）

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).

举例

s = “abc”, t = “ahbgdc”
Return true.
s = “axc”, t = “ahbgdc”
Return false.

思路

设置两个指针，i指向字符串t，j指向字符串s，遍历字符串t，若t[i]等于指针s[j]，则指针j向后移动一个位置；
若j指向字符串s最后一个位置的后一个位置（即字符串s已经遍历完毕），则返回true，若字符串t遍历完毕j仍未指向字符串s最后一个位置的后一个位置，则返回false。

代码

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