Added 10 solutions

General Programming/Basic Programming/Counting Valleys/Solution.java

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+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+
+// Idea: Keep track of your "level", which is how far above or below sea level you are.
+//       If you ever take a step up to sea level, you just completed walking through a valley.
+
+// Time Complexity: O(n)
+public class Solution {
+    public static void main(String[] args) {
+        /* Save input */
+        Scanner scan = new Scanner(System.in);
+        scan.nextLine();              // gets rid of 1st line
+        String str = scan.nextLine(); // String is of size "n"
+        scan.close();
+        
+        System.out.println(countValleys(str));
+    }
+    
+    private static int countValleys(String str) {
+        int level = 0;
+        int numValleys = 0;
+        for (int i = 0; i < str.length(); i++) {
+            char ch = str.charAt(i);
+            if (ch == 'U') {
+                level++;
+                if (level == 0) {
+                    numValleys++; // since we just stepped up to sea level
+                }
+            } else if (ch == 'D') {
+                level--;
+            }
+        }
+        return numValleys;
+    }
+}