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79 lines
2.2 KiB
Markdown
Executable File
79 lines
2.2 KiB
Markdown
Executable File
# [392. Is Subsequence](https://leetcode.com/problems/is-subsequence/)
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## 题目
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Given a string **s** and a string **t**, check if **s** is subsequence of **t**.
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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).
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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).
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**Example 1**:
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Input: s = "abc", t = "ahbgdc"
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Output: true
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**Example 2**:
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Input: s = "axc", t = "ahbgdc"
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Output: false
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**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?
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**Credits**: Special thanks to [@pbrother](https://leetcode.com/pbrother/) for adding this problem and creating all test cases.
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## 题目大意
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给定字符串 s 和 t ，判断 s 是否为 t 的子序列。你可以认为 s 和 t 中仅包含英文小写字母。字符串 t 可能会很长（长度 ~= 500,000），而 s 是个短字符串（长度 <=100）。字符串的一个子序列是原始字符串删除一些（也可以不删除）字符而不改变剩余字符相对位置形成的新字符串。（例如，"ace"是"abcde"的一个子序列，而"aec"不是）。
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## 解题思路
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- 给定 2 个字符串 s 和 t，问 s 是不是 t 的子序列。注意 s 在 t 中还需要保持 s 的字母的顺序。
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- 这是一题贪心算法。直接做即可。
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## 代码
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```go
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package leetcode
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// 解法一 O(n^2)
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func isSubsequence(s string, t string) bool {
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index, flag := 0, false
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for i := 0; i < len(s); i++ {
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flag = false
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for ; index < len(t); index++ {
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if s[i] == t[index] {
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flag = true
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break
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}
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}
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if flag == true {
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index++
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continue
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} else {
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return false
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}
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}
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return true
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}
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// 解法二 O(n)
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func isSubsequence1(s string, t string) bool {
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for len(s) > 0 && len(t) > 0 {
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if s[0] == t[0] {
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s = s[1:]
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}
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t = t[1:]
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}
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return len(s) == 0
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}
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``` |