5月场Java模拟考编程题

import java.util.Scanner;

/**
 * Created by zbyte on 17-5-19.
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int f = -1; // 标志: -1开始, 1递增, 2递减
        int last = sc.nextInt();
        int res = 0;
        for (int i = 1; i < n; i++) {
            int now = sc.nextInt();
            if (f == -1) {
                if (now > last) {
                    f = 1;
                } else if (now < last) {
                    f = 2;
                }
            } else if (f == 1) {
                if (now < last) {
                    f = -1;
                    res++;
                }
            } else {
                if (now > last) {
                    f = -1;
                    res++;
                }
            }
            last = now;
        }
        res++;

        System.out.println(res);
    }
}

import java.util.Arrays;
import java.util.Scanner;

/**
 * Created by zbyte on 17-5-19.
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int[] a = new int[n*3];
        for (int i = 0; i < n*3; i++) {
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        long res = 0;
        for (int i = n; i < n*3; i += 2) {
            res += a[i];
        }

        System.out.println(res);
    }
}

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

/**
 * Created by zbyte on 17-5-19.
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        Entity[] a = new Entity[n];
        for (int i = 0; i < n; i++) {
            a[i] = new Entity(sc.nextInt(), sc.nextInt());
        }

        Arrays.sort(a, new Comparator<Entity>() {
            @Override
            public int compare(Entity o1, Entity o2) {
                return o1.x-o2.x!=0 ? o1.x-o2.x : o1.y-o2.y;
            }
        });

        int max = 0; //x+y的最大值
        int index = 0; // 下标
        int cha = 0; // 差值
        for (int i = 0; i < n; i++) {
            if (a[i].x + a[i].y >= max || a[i].x + a[i].y + cha >= max) {
                max = a[i].x + a[i].y;
                cha = a[i].y - a[i].x;
                index = i;
            }
        }
        long res = max;
        for (int i = index-1; i >= 0 ; i--) {
            if (a[i].y > a[i].x) {
                res += a[i].y - a[i].x;
            }
        }

        System.out.println(res);
    }

    static class Entity {
        int x;
        int y;
        public Entity(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }
}