题解 | #合并表记录#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = Integer.valueOf(scan.nextLine().trim());
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        HashSet<Integer> hashSet = new HashSet<>();
        for (int i = 1; i <= n; i++) {
            String str = scan.nextLine();
            int index = Integer.valueOf(str.split(" ")[0].trim());
            int currentVal = Integer.valueOf(str.split(" ")[1].trim());
            int previousVal = hashMap.getOrDefault(index, 0);
            hashMap.put(index, previousVal + currentVal);
            hashSet.add(index);
        }
        ArrayList<Integer> arrayList = new ArrayList<>(hashSet);
        int[] nums = new int[arrayList.size()];
        for (int i = 0; i < arrayList.size(); i++) {
            nums[i] = arrayList.get(i);
        }
        heapSort(nums);
        for (int num : nums) {
            System.out.println(num + " " + hashMap.get(num));
        }
    }
    public static void heapSort(int[] nums) {
        if (null == nums || nums.length < 2) {
            return;
        }
        for (int i = 0; i < nums.length; i++) {
            heapInsert(nums, i);
        }
        int heapSize = nums.length;
        swap(nums, 0, --heapSize);
        while (heapSize > 0) {
            heapify(nums, 0, heapSize);
            swap(nums, 0, --heapSize);
        }
    }
    public static void heapInsert(int[] nums, int index) {
        while (nums[index] > nums[(index - 1) / 2]) {
            swap(nums, index, (index - 1) / 2);
            index = (index - 1) / 2;
        }
    }
    public static void heapify(int[] nums, int index, int heapSize) {
        int left = index * 2 + 1;
        while (left < heapSize) {
            int largest = left + 1 < heapSize && nums[left + 1] > nums[left] ? left + 1 : left;
            largest = nums[largest] > nums[index] ? largest : index;
            if (largest == index) {
                break;
            }
            swap(nums, index, largest);
            index = largest;
            left = index * 2 + 1;
        }
    }
    public static void swap(int[] nums, int p1, int p2) {
        int tmp = nums[p1];
        nums[p1] = nums[p2];
        nums[p2] = tmp;
    }
}