added some array datastructre algoritms

Author: VeeruYadav45

src/main/java/com/thealgorithms/datastructures/arrays/LeadersInArray.java

@@ -0,0 +1,46 @@
+package com.thealgorithms.datastructures.arrays;
+
+/**
+ * A program to find leaders in an array.
+ * 
+ * A leader is an element that is greater than all the elements to its right.
+ * The rightmost element is always a leader.
+ *
+ * Example:
+ * Input: [16, 17, 4, 3, 5, 2]
+ * Output: Leaders are 17, 5, 2
+ *
+ * Time Complexity: O(n)
+ * Space Complexity: O(1)
+ * 
+ * Author: https://github.com/VeeruYadav45
+ */
+public class LeadersInArray {
+
+    /**
+     * Prints all leader elements in the array.
+     *
+     * @param arr the input array
+     */
+    public static void findLeaders(int[] arr) {
+        int n = arr.length;
+
+        // The rightmost element is always a leader
+        int maxFromRight = arr[n - 1];
+        System.out.print("Leaders: " + maxFromRight + " ");
+
+        // Traverse the array from right to left
+        for (int i = n - 2; i >= 0; i--) {
+            if (arr[i] > maxFromRight) {
+                maxFromRight = arr[i]; // Update the new leader
+                System.out.print(maxFromRight + " ");
+            }
+        }
+    }
+
+    // Example usage
+    public static void main(String[] args) {
+        int[] arr = { 16, 17, 4, 3, 5, 2 };
+        findLeaders(arr);
+    }
+}

src/main/java/com/thealgorithms/datastructures/arrays/PeakElement.java

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+package com.thealgorithms.datastructures.arrays;
+
+/**
+ * A program to find a peak element in an array.
+ *
+ * <p>
+ * A peak element is an element that is greater than or equal to its neighbors.
+ * For corner elements, we need to consider only one neighbor.
+ *
+ * Example:
+ * Input: [1, 3, 20, 4, 1, 0]
+ * Output: Peak element is 20
+ *
+ * Time Complexity: O(log n) using binary search
+ * Space Complexity: O(1)
+ *
+ * Author: https://github.com/VeeruYadav45
+ */
+public class PeakElement {
+
+    /**
+     * Finds a peak element in the array using binary search.
+     *
+     * @param arr the input array
+     * @return the index of any one peak element
+     */
+    public static int findPeakElement(int[] arr) {
+        int n = arr.length;
+        int low = 0, high = n - 1;
+
+        while (low <= high) {
+            int mid = low + (high - low) / 2;
+
+            // Check if mid is a peak
+            boolean leftOk = (mid == 0) || (arr[mid] >= arr[mid - 1]);
+            boolean rightOk = (mid == n - 1) || (arr[mid] >= arr[mid + 1]);
+
+            if (leftOk && rightOk) {
+                return mid;
+            }
+
+            // If left neighbor is greater, move left
+            if (mid > 0 && arr[mid - 1] > arr[mid]) {
+                high = mid - 1;
+            } else { // Otherwise move right
+                low = mid + 1;
+            }
+        }
+
+        return -1; // Should never reach here if input is valid
+    }
+
+    // Example usage
+    public static void main(String[] args) {
+        int[] arr = { 1, 3, 20, 4, 1, 0 };
+        int peakIndex = findPeakElement(arr);
+        System.out.println("Peak element is " + arr[peakIndex]);
+    }
+}