Find max and min value by recursion

jonneyzhang · Sep 28, 2019 · 5043f89 · 5043f89
1 parent ff6b5c7
commit 5043f89
Show file tree

Hide file tree

Showing 2 changed files with 64 additions and 0 deletions.
diff --git a/Maths/FindMaxRecursion.java b/Maths/FindMaxRecursion.java
@@ -0,0 +1,32 @@
+package Maths;
+
+public class FindMaxRecursion {
+    public static void main(String[] args) {
+        int[] array = {2, 4, 9, 7, 19, 94, 5};
+        int low = 0;
+        int high = array.length - 1;
+
+        System.out.println("max value is " + max(array, low, high));
+    }
+
+    /**
+     * Get max of array using divide and conquer algorithm
+     *
+     * @param array contains elements
+     * @param low   the index of the first element
+     * @param high  the index of the last element
+     * @return max of {@code array}
+     */
+    public static int max(int[] array, int low, int high) {
+        if (low == high) {
+            return array[low]; //or array[high]
+        }
+
+        int mid = (low + high) >>> 1;
+
+        int leftMax = max(array, low, mid); //get max in [low, mid]
+        int rightMax = max(array, mid + 1, high); //get max in [mid+1, high]
+
+        return leftMax >= rightMax ? leftMax : rightMax;
+    }
+}
diff --git a/Maths/FindMinRecursion.java b/Maths/FindMinRecursion.java
@@ -0,0 +1,32 @@
+package Maths;
+
+public class FindMinRecursion {
+    public static void main(String[] args) {
+        int[] array = {2, 4, 9, 7, 19, 94, 5};
+        int low = 0;
+        int high = array.length - 1;
+
+        System.out.println("min value is " + min(array, low, high));
+    }
+
+    /**
+     * Get min of array using divide and conquer algorithm
+     *
+     * @param array contains elements
+     * @param low   the index of the first element
+     * @param high  the index of the last element
+     * @return min of {@code array}
+     */
+    public static int min(int[] array, int low, int high) {
+        if (low == high) {
+            return array[low]; //or array[high]
+        }
+
+        int mid = (low + high) >>> 1;
+
+        int leftMin = min(array, low, mid); //get min in [low, mid]
+        int rightMin = min(array, mid + 1, high); //get min in [mid+1, high]
+
+        return leftMin <= rightMin ? leftMin : rightMin;
+    }
+}