「力扣」第 195 场周赛代码（前 2 题）

比赛时间：北京时间 2020 年 6 月 28 日早 10:30

再接再厉！

第 1 题：判断路径是否相交

Java 代码：

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

public class Solution {

    public boolean isPathCrossing(String path) {
        Map<Character, int[]> directions = new HashMap<>();
        directions.put('N', new int[]{0, 1});
        directions.put('S', new int[]{0, -1});
        directions.put('E', new int[]{1, 0});
        directions.put('W', new int[]{-1, 0});

        char[] charArray = path.toCharArray();
        
        Set<Pair> visited = new HashSet<>();
        int currentX = 0;
        int currentY = 0;
        visited.add(new Pair(currentX, currentY));
        for (char c : charArray) {
            int[] direction = directions.get(c);
            int newX = currentX + direction[0];
            int newY = currentY + direction[1];

            boolean add = visited.add(new Pair(newX, newY));
            if (!add) {
                return true;
            }

            currentX = newX;
            currentY = newY;
        }
        return false;
    }

    class Pair {
        private int x;
        private int y;

        public Pair(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            Pair pair = (Pair) o;
            return x == pair.x && y == pair.y;
        }

        @Override
        public int hashCode() {
            return Objects.hash(x, y);
        }

        @Override
        public String toString() {
            return "Pair{" +
                    "x=" + x +
                    ", y=" + y +
                    '}';
        }
    }

    public static void main(String[] args) {
        Solution solution = new Solution();
        // String path = "NES";
        String path = "NESWW";
        boolean pathCrossing = solution.isPathCrossing(path);
        System.out.println(pathCrossing);
    }
}

第 2 题：检查数组对是否可以被 k 整除

import java.util.Arrays;

public class Solution {

    public boolean canArrange(int[] arr, int k) {
        int len = arr.length;
        int[] copy = new int[len];
        for (int i = 0; i < len; i++) {
            copy[i] = ((arr[i] % k) + k) % k;
        }
        Arrays.sort(copy);

        int left = 0;
        while (left < len && copy[left] == 0) {
            left++;
        }

        if (left % 2 == 1) {
            return false;
        }

        int right = len - 1;
        while (left < right) {
            if (copy[left] + copy[right] != k) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }

    public static void main(String[] args) {
//        int[] arr = {1, 2, 3, 4, 5, 10, 6, 7, 8, 9};
//        int k = 5;

//        int[] arr = {1, 2, 3, 4, 5, 6};
//        int k = 7;

//        int[] arr = {1, 2, 3, 4, 5, 6};
//        int k = 10;

//        int[] arr = {-10, 10};
//        int k = 2;


//        int[] arr = {-1, 1, -2, 2, -3, 3, -4, 4};
//        int k = 3;


        int[] arr = {-6, 2, 1, 1, 2, 2, 0, 0};
        int k = 2;


        Solution solution = new Solution();
        boolean res = solution.canArrange(arr, k);
        System.out.println(res);
    }
}