add order statistics

Author: zhangbo

src/algorithm/other/OrderStatistics.java

@@ -0,0 +1,114 @@
+package algorithm.other;
+
+import common.utils.ArrayUtils;
+
+/**
+ * Created by boyce on 2014/9/10.
+ */
+public class OrderStatistics<T extends Comparable> {
+
+    /**
+     * find min element from array
+     * @param array
+     * @return min element
+     * list all array to find min element, O(n)
+     */
+    public T findMin(T[] array) {
+        if (ArrayUtils.isEmpty(array))
+            return null;
+
+        if (array.length == 1)
+            return array[0];
+
+        T min = array[0];
+        for (int i=1; i<array.length; i++)
+            if (array[i].compareTo(min) < 0)
+                min = array[i];
+
+        return min;
+    }
+
+    /**
+     * find max element from array
+     * @param array
+     * @return max element
+     * list all array to find max element, O(n)
+     */
+    public T findMax(T[] array) {
+        if (ArrayUtils.isEmpty(array))
+            return null;
+
+        if (array.length == 1)
+            return array[0];
+
+        T max = array[0];
+        for (int i=1; i<array.length; i++)
+            if (array[i].compareTo(max) > 0)
+                max = array[i];
+
+        return max;
+    }
+
+    public T findArticleN(T[] array, int n) {
+        if (n >= array.length)
+            throw new ArrayIndexOutOfBoundsException("");
+
+        return this.findArticleN(array, 0, array.length-1, n);
+    }
+
+    /**
+     * find article n element from array
+     * @param array resource array
+     * @param p from p index in array
+     * @param q end q index in array
+     * @param i article i
+     * @return
+     */
+    private T findArticleN(T[] array, int p, int q, int i) {
+
+        if (p == q)
+            return array[p];
+
+        int t = this.partition(array, p, q);
+        if (t == i-1)
+            return array[t];
+
+        else if (t < i-1)
+            return findArticleN(array, t+1, q, i-t);
+
+        else
+            return findArticleN(array, p, t-1, i);
+    }
+
+    private int partition(T[] array, int p, int q) {
+        T x = array[q];
+        int i = p -1;
+        for (int j=p; j<q; j++) {
+            // if the target[j] < x , swap the index ++i element and index j element
+            if (array[j].compareTo(x) < 0) {
+                this.swap(array, ++i, j);
+
+                // if the target[j] >= x, do nothing, continue j++ to handle the next element
+            } else
+                ;
+
+        }
+        this.swap(array, i+1, q);
+
+        return i+1;
+    }
+
+    private void swap(T[] target, int p, int q) {
+        T temp = target[p];
+        target[p] = target[q];
+        target[q] = temp;
+    }
+
+    public static void main(String[] args) {
+        OrderStatistics<Integer> orderStatistics = new OrderStatistics<Integer>();
+        Integer[] array = {2, 3, 11, 4, 6, 2, 0, 13, 7, 9, 12};
+
+        System.out.println(orderStatistics.findMax(array));
+        System.out.println(orderStatistics.findMin(array));
+    }
+}