【JAVA】有赞2021校招数据笔试（B卷）——都是牛客原题

前言

这次的笔试题都是牛客原题哦，祝兄弟们都有心仪的offer

一、LRU（全A）

代码

package youzan;
package youzan;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashMap;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author: 
 * @Email: 
 * @Date: 2020/9/11
 * @Time: 15:34
 * @Version: 1.0
 * @Description: Description
 */
public class First {
    
    
    public static void main(String[] args) {
    
    
        int[][] matrix = new int[][]{
    
    {
    
    1, 1, 1}, {
    
    1, 2, 2}, {
    
    1, 3, 2}, {
    
    2, 1}, {
    
    1, 4, 4}, {
    
    2, 2}};
        System.out.println(Arrays.toString(LRU(matrix, 3)));
    }

    public static int[] LRU(int[][] operators, int k) {
    
    
        // write code here
        LinkedHashMap<Integer, Integer> lruMap = new LinkedHashMap<>();
        ArrayList<Integer> res = new ArrayList<>();

        for (int[] oper : operators) {
    
    
            int key = oper[1];
            switch (oper[0]) {
    
    
                case 1:
                    int value = oper[2];
                    if (lruMap.size() < k) {
    
    
                        lruMap.put(key, value);
                    } else {
    
    
                        Iterator it = lruMap.keySet().iterator();
                        lruMap.remove(it.next());
                        lruMap.put(key, value);
                    }
                    break;
                case 2:
                    if (lruMap.containsKey(key)) {
    
    
                        int val = lruMap.get(key);
                        res.add(val);
                        lruMap.remove(key);

                        lruMap.put(key, val);
                    } else {
    
    
                        res.add(-1);
                    }
                    break;
            }
        }
        int[] resArr = new int[res.size()];
        for (int i = 0; i < res.size(); i++) {
    
    
            resArr[i] = res.get(i);
        }
        return resArr;
    }
}

二、合法括号（全A）

代码

package youzan;

import java.util.Deque;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;

/**
 * Created by IntelliJ IDEA.
 *
 * @Author: 
 * @Email: 
 * @Date: 2020/9/11
 * @Time: 15:19
 * @Version: 1.0
 * @Description: Description
 */
public class Second {
    
    
    public static void main(String[] args) {
    
    
//        System.out.println(isVaild("123"));
        System.out.println(isVaild("(123)"));
    }

    public static boolean isVaild(String statement) {
    
    
        int len = statement.length();
        /*if ((len & 1) == 1) {
            return false;
        }*/
        Map<Character, Character> pairs = new HashMap<Character, Character>();
        pairs.put(')', '(');
        pairs.put(']', '[');
        pairs.put('}', '{');

        Deque<Character> stack = new LinkedList<>();
        for (int i = 0; i < len; i++) {
    
    
            char ch = statement.charAt(i);
            if (pairs.containsKey(ch)) {
    
    
                if (stack.isEmpty() || stack.peek() != pairs.get(ch)) {
    
    
                    return false;
                }
                stack.pop();
            } else if (ch == '(' || ch == '[' || ch == '{') {
    
    
                stack.push(ch);
            }
        }
        return stack.isEmpty();
    }
}