题解 | #合并表记录#

/*
 * 题目分析: 去重, 求和
 * 解题思路: 直接用HashMap, 不过HashMap是无序的, 提交一次试试, 过不了换TreeMap
 * 知识记录: TreeMap 默认排序规则：按照key的字典顺序来排序（升序）
 * 提交失败: HashMap果然不行, 换TreeMap吧
 */
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        TreeMap<Integer, Integer> map = new TreeMap();
        int count = sc.nextInt();
        for (int i = 0; i < count; i++) {
            int key = sc.nextInt();
            int val = sc.nextInt();
            if (map.containsKey(key)) {
                val += map.get(key);
            }
            map.put(key, val);
        }

        for (Map.Entry<Integer, Integer> e: map.entrySet()) {
            System.out.println(e.getKey() + " " + e.getValue());
        }
    }
}