README_EN.md

comments	difficulty	edit_url	rating	source	tags
true	Easy	https://github.com/doocs/leetcode/edit/main/solution/2800-2899/2810.Faulty%20Keyboard/README_EN.md	1192	Weekly Contest 357 Q1	String Simulation

2810. Faulty Keyboard

中文文档

Description

Your laptop keyboard is faulty, and whenever you type a character 'i' on it, it reverses the string that you have written. Typing other characters works as expected.

You are given a 0-indexed string s, and you type each character of s using your faulty keyboard.

Return the final string that will be present on your laptop screen.

 

Example 1:

Input: s = "string"
Output: "rtsng"
Explanation: 
After typing first character, the text on the screen is "s".
After the second character, the text is "st". 
After the third character, the text is "str".
Since the fourth character is an 'i', the text gets reversed and becomes "rts".
After the fifth character, the text is "rtsn". 
After the sixth character, the text is "rtsng". 
Therefore, we return "rtsng".

Example 2:

Input: s = "poiinter"
Output: "ponter"
Explanation: 
After the first character, the text on the screen is "p".
After the second character, the text is "po". 
Since the third character you type is an 'i', the text gets reversed and becomes "op". 
Since the fourth character you type is an 'i', the text gets reversed and becomes "po".
After the fifth character, the text is "pon".
After the sixth character, the text is "pont". 
After the seventh character, the text is "ponte". 
After the eighth character, the text is "ponter". 
Therefore, we return "ponter".

 

Constraints:

• 1 <= s.length <= 100
• s consists of lowercase English letters.
• s[0] != 'i'

Solutions

Solution 1: Simulation

We directly simulate the keyboard input process, using a character array $t$ to record the text on the screen, initially $t$ is empty.

For each character $c$ in string $s$, if $c$ is not the character $'i'$, then we add $c$ to the end of $t$; otherwise, we reverse all characters in $t$.

The final answer is the string composed of characters in $t$.

The time complexity is $O(n^2)$, and the space complexity is $O(n)$, where $n$ is the length of string $s$.

Python3

class Solution:
    def finalString(self, s: str) -> str:
        t = []
        for c in s:
            if c == "i":
                t = t[::-1]
            else:
                t.append(c)
        return "".join(t)

Java

class Solution {
    public String finalString(String s) {
        StringBuilder t = new StringBuilder();
        for (char c : s.toCharArray()) {
            if (c == 'i') {
                t.reverse();
            } else {
                t.append(c);
            }
        }
        return t.toString();
    }
}

C++

class Solution {
public:
    string finalString(string s) {
        string t;
        for (char c : s) {
            if (c == 'i') {
                reverse(t.begin(), t.end());
            } else {
                t.push_back(c);
            }
        }
        return t;
    }
};

Go

func finalString(s string) string {
	t := []rune{}
	for _, c := range s {
		if c == 'i' {
			for i, j := 0, len(t)-1; i < j; i, j = i+1, j-1 {
				t[i], t[j] = t[j], t[i]
			}
		} else {
			t = append(t, c)
		}
	}
	return string(t)
}

TypeScript

function finalString(s: string): string {
    const t: string[] = [];
    for (const c of s) {
        if (c === 'i') {
            t.reverse();
        } else {
            t.push(c);
        }
    }
    return t.join('');
}

Rust

impl Solution {
    pub fn final_string(s: String) -> String {
        let mut t = Vec::new();
        for c in s.chars() {
            if c == 'i' {
                t.reverse();
            } else {
                t.push(c);
            }
        }
        t.into_iter().collect()
    }
}