CountingValleys.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    // Complete the countingValleys function below.
    static int countingValleys(int n, String s) {
        ArrayList<Integer> path = new ArrayList<Integer>();
        path.add(0);

        for(int i = 0; i < n; i++)              // detecting highs and lows in path
        {
            if(s.charAt(i) == 'U')
            {
                path.add(path.get(i) + 1);
            }
            else if(s.charAt(i) == 'D')
            {
                path.add(path.get(i) - 1);
            }
        }
        path.add(0);
        
        int numValleys = 0;
        for(int j = 1; j < n+2; j++)           // detecting valleys
        {
            if(path.get(j-1) < 0 && path.get(j) == 0)
            {
                numValleys++;
            }
        }
        return numValleys;

    }

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

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

        int n = scanner.nextInt();
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        String s = scanner.nextLine();

        int result = countingValleys(n, s);

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

        bufferedWriter.close();

        scanner.close();
    }
}