🍱 exercise;

cdToucher · cdToucher · commit 39ff61b47787 · 2018-01-17T14:14:40.000+08:00
diff --git a/src/me/codebase/leetcode/algo/MergeSort.java b/src/me/codebase/leetcode/algo/MergeSort.java
@@ -0,0 +1,54 @@
+package me.codebase.leetcode.algo;
+
+import java.util.Arrays;
+
+/**
+ * Created by chendong on 2018/1/12.
+ */
+public class MergeSort implements Sort {
+
+
+    public static void main(String[] args) {
+//        sort(arr);
+        System.out.println(Arrays.toString(new MergeSort().sort(arr)));
+    }
+
+/*    public int[] sort(int[] a){
+        int[] h = a.clone();
+        return a;
+    }*/
+
+
+
+    public int[] sort(int[] a) {
+        int[] helper = a.clone();
+        sort(a, 0, a.length - 1, helper);
+        return arr;
+    }
+
+    private static void sort(int[] a, int lo, int hi, int[] helper) {
+        if (lo >= hi) return;
+        int mid = (lo + hi) / 2;
+        sort(a, lo, mid, helper);
+        sort(a, mid + 1, hi, helper);
+        merge(a, lo, mid, hi, helper);
+    }
+
+    private static void merge(int[] a, int lo, int mid, int hi, int[] helper) {
+
+        System.arraycopy(a, lo, helper, lo, hi + 1 - lo);
+        int i = lo;
+        int j = mid + 1;
+        for (int k = lo; k <= hi; k++) {
+            if (i > mid)
+                a[k] = helper[j++];
+            else if (j > hi)
+                a[k] = helper[i++];
+            else if (helper[i] <= helper[j])
+                a[k] = helper[i++];
+            else
+                a[k] = helper[j++];
+        }
+
+    }
+}
diff --git a/src/me/codebase/leetcode/algo/QuickSort.java b/src/me/codebase/leetcode/algo/QuickSort.java
@@ -5,9 +5,8 @@
 /**
  * Created by chendong on 2018/1/11.
  */
-public class QuickSort {
+public class QuickSort implements Sort{
 
-    private static final int[] arr = {0, 2, 4, 6, 8, 5, 3, 7, 9, 1, 400};
 
     public static void main(String[] args) {
         System.out.println(Arrays.toString(new QuickSort().sort(arr)));
diff --git a/src/me/codebase/leetcode/algo/Sort.java b/src/me/codebase/leetcode/algo/Sort.java
@@ -0,0 +1,10 @@
+package me.codebase.leetcode.algo;
+
+/**
+ * Created by chendong on 2018/1/12.
+ */
+public interface Sort {
+
+     int[] arr = {0, 2, 4, 6, 8, 5, 3, 7, 9, 1, 400};
+
+}
diff --git a/src/me/codebase/leetcode/algo/TreeBuilder.java b/src/me/codebase/leetcode/algo/TreeBuilder.java
@@ -0,0 +1,13 @@
+package me.codebase.leetcode.algo;
+
+import me.codebase.leetcode.structure.TreeNode;
+
+/**
+ * Created by chendong on 2018/1/12.
+ */
+public class TreeBuilder {
+
+    public static TreeNode getRootNode(){
+        return null;
+    }
+}
