LeetCode 2231: Largest Number After Digit Swaps by Parity Solution

Master LeetCode problem 2231 (Largest Number After Digit Swaps by Parity), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2231. Largest Number After Digit Swaps by Parity

Easy

Sorting Heap (Priority Queue)

Problem Explanation

Explanation

To find the largest possible value of the given number after swapping digits with the same parity, we can follow these steps:

Separate the digits of the number into two lists, one for even digits and one for odd digits.
Sort both lists in descending order.
Combine the digits from both lists to form the largest number while ensuring that we swap digits only within the same parity group.

Time complexity: O(n log n) where n is the number of digits in the input number. Space complexity: O(n)

Solution Code

class Solution {
    public int maximumSwap(int num) {
        char[] digits = String.valueOf(num).toCharArray();
        int[] lastIndexes = new int[10];
        
        for (int i = 0; i < digits.length; i++) {
            lastIndexes[digits[i] - '0'] = i;
        }
        
        for (int i = 0; i < digits.length; i++) {
            for (int j = 9; j > digits[i] - '0'; j--) {
                if (lastIndexes[j] > i) {
                    char temp = digits[i];
                    digits[i] = digits[lastIndexes[j]];
                    digits[lastIndexes[j]] = temp;
                    return Integer.parseInt(new String(digits));
                }
            }
        }
        
        return num;
    }
}

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