README_EN.md

comments	difficulty	edit_url	rating	source	tags
true	Easy	https://github.com/doocs/leetcode/edit/main/solution/1500-1599/1544.Make%20The%20String%20Great/README_EN.md	1344	Weekly Contest 201 Q1	Stack String

1544. Make The String Great

中文文档

Description

Given a string s of lower and upper case English letters.

A good string is a string which doesn't have two adjacent characters s[i] and s[i + 1] where:

• 0 <= i <= s.length - 2
• s[i] is a lower-case letter and s[i + 1] is the same letter but in upper-case or vice-versa.

To make the string good, you can choose two adjacent characters that make the string bad and remove them. You can keep doing this until the string becomes good.

Return the string after making it good. The answer is guaranteed to be unique under the given constraints.

Notice that an empty string is also good.

 

Example 1:

Input: s = "leEeetcode"
Output: "leetcode"
Explanation: In the first step, either you choose i = 1 or i = 2, both will result "leEeetcode" to be reduced to "leetcode".

Example 2:

Input: s = "abBAcC"
Output: ""
Explanation: We have many possible scenarios, and all lead to the same answer. For example:
"abBAcC" --> "aAcC" --> "cC" --> ""
"abBAcC" --> "abBA" --> "aA" --> ""

Example 3:

Input: s = "s"
Output: "s"

 

Constraints:

• 1 <= s.length <= 100
• s contains only lower and upper case English letters.

Solutions

Solution 1

Python3

class Solution:
    def makeGood(self, s: str) -> str:
        stk = []
        for c in s:
            if not stk or abs(ord(stk[-1]) - ord(c)) != 32:
                stk.append(c)
            else:
                stk.pop()
        return "".join(stk)

Java

class Solution {
    public String makeGood(String s) {
        StringBuilder sb = new StringBuilder();
        for (char c : s.toCharArray()) {
            if (sb.length() == 0 || Math.abs(sb.charAt(sb.length() - 1) - c) != 32) {
                sb.append(c);
            } else {
                sb.deleteCharAt(sb.length() - 1);
            }
        }
        return sb.toString();
    }
}

C++

class Solution {
public:
    string makeGood(string s) {
        string stk;
        for (char c : s) {
            if (stk.empty() || abs(stk.back() - c) != 32) {
                stk += c;
            } else {
                stk.pop_back();
            }
        }
        return stk;
    }
};

Go

func makeGood(s string) string {
	stk := []rune{}
	for _, c := range s {
		if len(stk) == 0 || abs(int(stk[len(stk)-1]-c)) != 32 {
			stk = append(stk, c)
		} else {
			stk = stk[:len(stk)-1]
		}
	}
	return string(stk)
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}