https://www.hackerrank.com/challenges/counting-valleys/problem?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=warmup

Result.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

    /*
     * Complete the 'countingValleys' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts following parameters:
     *  1. INTEGER steps
     *  2. STRING path
     */

    public static int countingValleys(int steps, String path) {
        int count = 0;
        int level = 0;
        for (int i = 0; i < steps; i++){
            if ((level == 0) && (path.charAt(i) == 'D')){
                count++;
            }
            if (path.charAt(i) == 'U'){
                level++;
            } else {
                level--;
            }
        }
        return count;

    }

}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int steps = Integer.parseInt(bufferedReader.readLine().trim());

        String path = bufferedReader.readLine();

        int result = Result.countingValleys(steps, path);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}