Problem

Solution

package org.span;

import java.io.IOException;
import java.util.Scanner;

public class HourGlass {

    static int hourglassSum(int[][] arr) {
        int max = -99999, cur;
        for (int i = 0; i < 4; i++) {
            for (int j = 0; j < 4; j++) {
                cur = arr[i][j] + arr[i][j + 1] + arr[i][j + 2] + arr[i + 1][j + 1] + arr[i + 2][j] + arr[i + 2][j + 1] + arr[i + 2][j + 2];
                if (cur > max) {
                    max = cur;
                }
            }
        }
        return max;
    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        /*int[][] arr = {
                {1, 1, 1, 0, 0, 0},
                {0, 1, 0, 0, 0, 0},
                {1, 1, 1, 0, 0, 0},
                {0, 0, 2, 4, 4, 0},
                {0, 0, 0, 2, 0, 0},
                {0, 0, 1, 2, 4, 0}
        };*/
        int[][] arr = {
                {0, -4, -6, 0, -7, -6},
                {-1, -2, -6, -8, -3, -1},
                {-8, -4, -2, -8, -8, -6},
                {-3, -1, -2, -5, -7, -4},
                {-3, -5, -3, -6, -6, -6},
                {-3, -6, 0, -8, -6, -7},
        };
        int result = hourglassSum(arr);
        System.out.println(result);
    }
}

Problem

Solution

import java.io.IOException;

public class RepeatedString {
    static long repeatedString(String s, long n) {
        long noOfOccurence = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == 'a')
                noOfOccurence++;
        }
        long repeat = n / s.length();
        noOfOccurence *= repeat;
        for (int i = 0; i < n % s.length(); i++) {
            if (s.charAt(i) == 'a')
                noOfOccurence++;
        }
        return noOfOccurence;
    }

    public static void main(String[] args) throws IOException {
        String s = "aba";
        long n = 10;
        long result = repeatedString(s, n);
        System.out.println(result);
    }
}

Problem

Solution

import java.io.IOException;

public class JumpingOnClouds {
    static int jumpingOnClouds(int[] c) {
        int jumps = 0;
        for (int i = 0; i < c.length; ) {
            if (i + 2 < c.length && c[i + 2] == 0)
                i += 2;
            else
                i++;
            jumps++;
        }
        return jumps - 1;
    }

    public static void main(String[] args) throws IOException {
        int[] c = {0, 0, 1, 0, 0, 1, 0};
        int result = jumpingOnClouds(c);
        System.out.println(result);
    }
}

Problem

Solution

import java.io.IOException;

class Result {
    public static int countingValleys(int steps, String path) {
        int valleyCount = 0, prePos, pos = 0;
        for (int i = 0; i < steps; i++) {
            prePos = pos;
            if (path.charAt(i) == 'D')
                pos--;
            else
                pos++;
            if (pos == 0 & prePos < 0)
                valleyCount++;
        }
        return valleyCount;
    }
}

public class CountingValleys {
    public static void main(String[] args) throws IOException {
        int steps = 8;
        String path = "UDDDUDUU";
        int result = Result.countingValleys(steps, path);
        System.out.println(result);
    }
}

Problem

Alex works at a clothing store. There is a large pile of socks that must be paired by color for sale.
Given an array of integers representing the color of each sock, determine how many pairs of socks with matching colors there are.

For example, there are n=7 socks with colors ar = [1,2,1,2,1,3,2] .
There is one pair of color 1 and one of color 2.
There are three odd socks left, one of each color. The number of pairs is 2.

Function Description
Complete the sockMerchant function in the editor below.
It must return an integer representing the number of matching pairs of socks that are available.

sockMerchant has the following parameter(s):
n: the number of socks in the pile
ar: the colors of each sock

Input Format
The first line contains an integer n, the number of socks represented in ar.
The second line contains n space-separated integers describing the colors ar[i] of the socks in the pile.

Constraints
1 <= n <= 100
1 <= ar[i] <= 100 where 0 <= i < n

Output Format
Return the total number of matching pairs of socks that Alex can sell.

Sample Input
9
10 20 20 10 10 30 50 10 20

Sample Output
3

Alex can match three pairs of socks

Solution

import java.util.HashMap;
import java.util.Scanner;

public class PairOfSocks {
    static int sockMerchant(int n, int[] ar) {
        HashMap<Integer, Integer> colorsMap = new HashMap<>();
        for (int color : ar) {
            colorsMap.put(color, (colorsMap.getOrDefault(color, 0)) + 1);
        }
        final int[] totalPair = {0};
        colorsMap.forEach((key, value) -> totalPair[0] += value / 2);
        return totalPair[0];
    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        int n = scanner.nextInt();
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
        int[] ar = new int[n];
        String[] arItems = scanner.nextLine().split(" ");
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        for (int i = 0; i < n; i++) {
            int arItem = Integer.parseInt(arItems[i]);
            ar[i] = arItem;
        }
        int result = sockMerchant(n, ar);
        System.out.println(result);
        scanner.close();
    }
}

Explanation

We need to find no of pairs for each number. We can add the quantity of each number into a map. Then we can divide the values by 2 and sum up to get the final answer.