题解 | 选药

import java.util.StringTokenizer;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;

// 药品类，语义化命名
class Drug {
    int pain; // 疼痛程度，语义化命名
    int effect; // 功效值，语义化命名

    public Drug(int pain, int effect) {
        this.pain = pain;
        this.effect = effect;
    }
}

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

        // 读取药品数量
        int n = Integer.parseInt(br.readLine());
        Drug[] drugs = new Drug[n];
        for (int i = 0; i < n; i++) {
            StringTokenizer st = new StringTokenizer(br.readLine());
            int pain = Integer.parseInt(st.nextToken());
            int effect = Integer.parseInt(st.nextToken());
            drugs[i] = new Drug(pain, effect);
        }

        // 按疼痛程度升序排序，使用Integer.compare避免溢出
        Arrays.sort(drugs, (a, b) -> Integer.compare(a.pain, b.pain));

        // 构建疼痛值数组和前缀最大功效值数组
        int[] painArr = new int[n];
        int[] maxEffect = new int[n];
        for (int i = 0; i < n; i++) {
            painArr[i] = drugs[i].pain;
            if (i == 0) {
                maxEffect[i] = drugs[i].effect;
            } else {
                maxEffect[i] = Math.max(maxEffect[i - 1], drugs[i].effect);
            }
        }

        // 处理查询
        int q = Integer.parseInt(br.readLine());
        for (int i = 0; i < q; i++) {
            int x = Integer.parseInt(br.readLine()); // 疼痛忍耐度
            int left = 0, right = n - 1;
            int index = -1;

            // 二分查找最大的不超过x的疼痛值索引
            while (left <= right) {
                int mid = (left + right) >>> 1;
                if (painArr[mid] <= x) {
                    index = mid;
                    left = mid + 1;
                } else {
                    right = mid - 1;
                }
            }

            // 输出结果
            if (index == -1) {
                pw.println(-1);
            } else {
                pw.println(maxEffect[index]);
            }
        }

        // 关闭资源
        br.close();
        pw.close();
    }
}