LeetCode Biweekly Contest 172 Discussion and Solution

Problem-by-Problem Breakdown

Problem 1 - Minimum Number of Operations to Have Distinct Elements

Approach

Java Code

class Solution {
    public int minOperations(int[] nums) {
        int n = nums.length;

        Map<Integer, Integer> map = new HashMap<>();

        int i = 0;
        int ans = 0;
        int duplicateCount = 0;

        for(int num : nums){
            map.put(num, map.getOrDefault(num, 0) + 1);

            if(map.get(num) == 2){
                duplicateCount++;
            }
        }


        while(i < n && duplicateCount > 0){
            for(int j = 0; j < 3 && i < n; j++, i++){
                map.put(nums[i], map.get(nums[i]) - 1);
                if(map.get(nums[i]) == 1) duplicateCount--;
            }
            ans++;
        }

        return ans;   
    }
}

Problem 2 - Maximum Sum of Three Numbers Divisible by Three

Approach

Java Code

class Solution {
    public int maximumSum(int[] nums) {
        Arrays.sort(nums);

        int n = nums.length;

        int[] zero = new int[3];
        int[] one = new int[3];
        int[] two = new int[3];

        int i = 2;
        int j = 2;
        int k = 2;

        for(int l = n - 1; l >= 0; l--){
            int rem = nums[l] % 3;

            if(rem == 0 && i >= 0){
                zero[i] = nums[l];
                i--;
            }
            else if(rem == 1 && j >= 0){
                one[j] = nums[l];
                j--;
            }
            else if(rem == 2 && k >= 0){
                two[k] = nums[l];
                k--;
            }
        }

        int max = 0;

        max = i >= 0 ? max : Math.max(max, zero[0] + zero[1] + zero[2]);
        max = j >= 0 ? max : Math.max(max, one[0] + one[1] + one[2]);
        max = k >= 0 ? max : Math.max(max, two[0] + two[1] + two[2]);
        if(i < 2 && j < 2 && k < 2){
            max = Math.max(max, zero[2] + one[2] + two[2]);
        }

        return max;
    }
}

Problem 3 - Maximum Score After Binary Swaps

Approach

Java Code

class Solution {
    public long maximumScore(int[] nums, String s) {
        int n = nums.length;

        PriorityQueue<Integer> queue = new PriorityQueue<>((a, b) -> b - a);
        long ans = 0;

        for(int i = 0; i < n; i++){
            queue.add(nums[i]);
            if(s.charAt(i) == '1') ans += queue.poll();
        }

        return ans;
    }
}

Problem 4 - Last Remaining Integer After Alternating Deletion Operations

• Operation 1: Starting from the left, delete every second number.
• Operation 2: Starting from the right, delete every second number.

Approach

My Contest Experience