LeetCode - 5. Longest Palindromic Substring

문제 링크입니다 : https://leetcode.com/problems/longest-palindromic-substring/

Longest Palindromic Substring - LeetCode

 

 

 

 

 

 

 

C++

class Solution {
public:
    string longestPalindrome(string s) {
        string result = "";
        int maxLength = 0;
        
        if (s.size() == 1) {
            return s;
        }
        
        for (int i = 0; i < s.size() - 1; i++) {
            int leftIndex = i;
            int rightIndex = i;
            int cnt = 1;
            while (true) {
                leftIndex--;
                rightIndex++;

                if (leftIndex < 0 || rightIndex == s.size() || s[leftIndex] != s[rightIndex]) {
                    if (cnt > maxLength) {
                        maxLength = cnt;
                        result = s.substr(leftIndex + 1, rightIndex - leftIndex - 1);
                    }
                    break;
                }
                cnt += 2;
            }
            
            leftIndex = i;
            rightIndex = i + 1;
            cnt = 0;
            while (true) {
                if (leftIndex < 0 || rightIndex == s.size() || s[leftIndex] != s[rightIndex]) {
                    if (cnt > maxLength) {
                        maxLength = cnt;
                        result = s.substr(leftIndex + 1, rightIndex - leftIndex - 1);
                    }
                    break;
                }
                cnt += 2;
                leftIndex--;
                rightIndex++;
            }
            
        }
        return result;
    }
};

 

 

 

 

 

 

JAVA

class Solution {
    public String longestPalindrome(String s) {
        String result = "";
        int maxLength = 0;
        
        if (s.length() == 1) {
            return s;
        }
        
        for (int i = 0; i < s.length() - 1; i++) {
            int leftIndex = i;
            int rightIndex = i;
            int cnt = 1;
            while(true) {
                leftIndex--;
                rightIndex++;
                if (leftIndex < 0 || rightIndex == s.length() || s.charAt(leftIndex) != s.charAt(rightIndex)) {
                    if (cnt > maxLength) {
                        maxLength = cnt;
                        result = s.substring(leftIndex + 1, rightIndex);
                    }
                    break;
                }
                cnt += 2;
            }
            
            leftIndex = i;
            rightIndex = i + 1;
            cnt = 0;
            
            while(true) {
                if (leftIndex < 0 || rightIndex == s.length() || s.charAt(leftIndex) != s.charAt(rightIndex)) {
                    if (cnt > maxLength) {
                        maxLength = cnt;
                        result = s.substring(leftIndex + 1, rightIndex);
                    }
                    break;
                }
                cnt += 2;
                leftIndex--;
                rightIndex++;
            }    
        }
        
        return result;
    }
}

 

 

 

 

 

 

Python3

class Solution:
    def longestPalindrome(self, s: str) -> str:
        result = ''
        maxLen = 0
        s_len = len(s)
        
        if s_len == 1:
            return s
        
        for i in range(s_len - 1):
            left_index = i
            right_index = i
            cnt = 1
            
            while True:
                left_index -= 1
                right_index += 1
                if left_index < 0 or right_index == s_len or s[left_index] != s[right_index]:
                    if cnt > maxLen:
                        maxLen = cnt
                        result = s[left_index + 1 : right_index]
                    break
                cnt += 2
            
            left_index = i
            right_index = i + 1
            cnt = 0
            
            while True:
                if left_index < 0 or right_index == s_len or s[left_index] != s[right_index]:
                    if cnt > maxLen:
                        maxLen = cnt
                        result = s[left_index + 1 : right_index]
                    break
                left_index -= 1
                right_index += 1
                cnt += 2
            
        return result

 

 

 

 

 

 

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