2390-RemovingStarsFromAString.go

package main

// 2390. Removing Stars From a String
// You are given a string s, which contains stars *.
// In one operation, you can:
//     Choose a star in s.
//     Remove the closest non-star character to its left, as well as remove the star itself.

// Return the string after all stars have been removed.
// Note:
//     The input will be generated such that the operation is always possible.
//     It can be shown that the resulting string will always be unique.
    
// Example 1:
// Input: s = "leet**cod*e"
// Output: "lecoe"
// Explanation: Performing the removals from left to right:
// - The closest character to the 1st star is 't' in "leet**cod*e". s becomes "lee*cod*e".
// - The closest character to the 2nd star is 'e' in "lee*cod*e". s becomes "lecod*e".
// - The closest character to the 3rd star is 'd' in "lecod*e". s becomes "lecoe".
// There are no more stars, so we return "lecoe".

// Example 2:
// Input: s = "erase*****"
// Output: ""
// Explanation: The entire string is removed, so we return an empty string.
 
// Constraints:
//     1 <= s.length <= 10^5
//     s consists of lowercase English letters and stars *.
//     The operation above can be performed on s.

import "fmt"

// stack
func removeStars(s string) string {
    res := []byte{}
    for i := 0; i < len(s); i++ {
        if s[i] == '*' { // 遇见 * pop出一个字符
            if len(res) > 0 {
                res = res[:len(res) - 1]
            }
        } else {
            res = append(res, s[i]) // 入栈
        }
    }
    return string(res)
}

func main() {
    // Example 1:
    // Input: s = "leet**cod*e"
    // Output: "lecoe"
    // Explanation: Performing the removals from left to right:
    // - The closest character to the 1st star is 't' in "leet**cod*e". s becomes "lee*cod*e".
    // - The closest character to the 2nd star is 'e' in "lee*cod*e". s becomes "lecod*e".
    // - The closest character to the 3rd star is 'd' in "lecod*e". s becomes "lecoe".
    // There are no more stars, so we return "lecoe".
    fmt.Println(removeStars("leet**cod*e")) // lecoe
    // Example 2:
    // Input: s = "erase*****"
    // Output: ""
    // Explanation: The entire string is removed, so we return an empty string.
    fmt.Println(removeStars("erase*****")) // ""
}