Repeat & Missing Number

import java.util.*;

public class RepeatAndMissingNumber {
    public static int[] findRepeatAndMissing(int[] arr) {
        int n = arr.length;
        Map<Integer, Integer> map = new HashMap<>();
        int[] result = new int[2]; // result[0] = repeated, result[1] = missing
        
        // Count occurrences manually using containsKey()
        for (int num : arr) {
            if (map.containsKey(num)) {
                map.put(num, map.get(num) + 1); // Increment count if already present
            } else {
                map.put(num, 1); // Insert with count 1 if not present
            }
        }

        // Identify repeated and missing numbers
        for (int i = 1; i <= n; i++) {
            if (map.containsKey(i)) {
                if (map.get(i) > 1) {
                    result[0] = i; // Repeated number
                }
            } else {
                result[1] = i; // Missing number
            }
        }
        
        return result;
    }

    public static void main(String[] args) {
        int[] arr = {3, 1, 2, 5, 3}; // Example: 3 is repeated, 4 is missing
        int[] ans = findRepeatAndMissing(arr);
        System.out.println("Repeated: " + ans[0] + ", Missing: " + ans[1]);
    }
}