爱健身的小王, 修改矩阵,最长上升子串 -美团2019笔试题

爱健身的小王-美团2019笔试题

一、暴力解法：
((n+1) *k) % 4n = n+1 ，k>= 2, 枚举出最小符合条件的k。

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        while(t-- > 0) {
            int n = sc.nextInt();
            int sq = 4 * n;
            int step = n + 1;
            for(int i=2; ; i++) {
                if((step*i) % sq == step) {
                    System.out.println(i);
                    break;
                }
            }
        }
    }
}

解法二、最大公约数解法

[(n+1)x = 4n y ag {1} ]

[x =dfrac{[n+1, 4n]}{n+1} = dfrac{(n+1)(4n)}{(4n,n+1)(n+1)}= dfrac{4n}{(n+1, 4n)} ag{2} ]

标记x次，刚好跑了y圈，则答案为x+1。根据公式（2）可以推导出最小x的值（x >= 2）。

import java.util.*;
public class Main {
    static int gcd(int a, int b) {
        return b == 0 ? a : gcd(b, a%b);
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        while(t-- > 0) {
            int n = sc.nextInt();
            int sq = 4 * n;
            int step = n + 1;
            int res = sq / gcd(sq,step) + 1;
            System.out.println(res);
        }
    }
}

修改矩阵

细节要爆炸！！！

import java.util.*;
public class Main{
    static int[][] getTopTwo(Map<Integer, Integer> map) {
        int[][] res = new int[map.size()][2];
        int idx = 0;
        for(int k : map.keySet()) {
            res[idx][0] = k; res[idx][1] = map.get(k); idx ++; 
        }
        Arrays.sort(res, (o1, o2)->o2[1]-o1[1]);
        return res;
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt(), m = sc.nextInt();
        Map<Integer, Integer> map1 = new HashMap<>();
        Map<Integer, Integer> map2 = new HashMap<>();
        
        for(int i=0; i < n; i++) {
            for(int j=0; j < m; j++) {
                int t = sc.nextInt();
                if((i+j) % 2 == 0) 
                    map1.put(t, map1.getOrDefault(t, 0) + 1);
                else
                    map2.put(t, map2.getOrDefault(t, 0) + 1);
            }
        }
        int[][] a = getTopTwo(map1);
        int[][] b = getTopTwo(map2);
        int res = 0;
        for(int i=0; i < 2 && i < map1.size(); i++)
            for(int j=0; j < 2 && j < map2.size(); j++) 
                if(a[i][0] == b[j][0]) 
                    res = Math.max(res, Math.max(a[i][1], b[j][1]));
                else 
                    res = Math.max(res, a[i][1] + b[j][1]);
        
        if(a[0][0] == 0) res = b[0][1];
        if(b[0][0] == 0) res = a[0][1];
        // System.out.println(Arrays.deepToString(a));
        // System.out.println(Arrays.deepToString(b));
        System.out.println(m*n - res);
    }
}

最长上升子串

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] nums = new int[n];
        List<Integer> re = new ArrayList<>();
        for(int i=0; i < n; i++) {
            nums[i] = sc.nextInt();
            if(i >= 1 && nums[i-1] >= nums[i]) re.add(i); 
        }
        if(re.size() == 0) {
            System.out.println(n-1); 
        } else {
            int res = 0;
            int s1 = 0;
            for(int i=0; i < re.size(); i++) {
                int s2 = re.get(i);
                int l1 = s2 - s1;
                int s3 = i+1 < re.size() ? re.get(i+1) : n;
                int l2 = s3 - s2;
                int t = Math.max(l1, l2);
                if((l2 > 1 && nums[s2-1] < nums[s2+1]) 
                    || (l1 > 1 && nums[s2-2] < nums[s2])) {
                        t = l1 + l2 - 1;
                }
                if(t > res) res = t;
                s1 = s2;
            }
            System.out.println(res);
        }
    }
}