refactor 120

fishercoder1534 · fishercoder1534 · commit 8829017d4f6c · 2018-04-04T08:01:57.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_120.java b/src/main/java/com/fishercoder/solutions/_120.java
@@ -1,10 +1,11 @@
 package com.fishercoder.solutions;
 
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 
-/**Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.
+/**
+ * 120. Triangle
+
+  Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.
 
  For example, given the following triangle
  [
@@ -17,31 +18,22 @@
 
  Note:
  Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.*/
-public class _120 {
 
-    public static int minimumTotal(List<List<Integer>> triangle) {
-        /**https://discuss.leetcode.com/topic/1669/dp-solution-for-triangle, @stellari has a very excellent explanation.
-         * Basically, we use the bottom-up approach, starting from the bottom row of this triangle, and we only need to store the shortest path of each node
-         * from its last row, and keep overwriting it until we reach the top.*/
-        int n = triangle.size();
-        List<Integer> cache = triangle.get(n - 1);
-
-        for (int layer = n - 2; layer >= 0; layer--) {
-            //for each layer
-            for (int i = 0; i <= layer; i++) {
-                //check its very node
-                int value = Math.min(cache.get(i), cache.get(i + 1)) + triangle.get(layer).get(i);
-                cache.set(i, value);
-            }
+public class _120 {
+  public static class Solution1 {
+    public int minimumTotal(List<List<Integer>> triangle) {
+      int n = triangle.size();
+      List<Integer> cache = triangle.get(n - 1);
+
+      for (int layer = n - 2; layer >= 0; layer--) {
+        //for each layer
+        for (int i = 0; i <= layer; i++) {
+          //check its very node
+          int value = Math.min(cache.get(i), cache.get(i + 1)) + triangle.get(layer).get(i);
+          cache.set(i, value);
         }
-        return cache.get(0);
+      }
+      return cache.get(0);
     }
-
-    public static void main(String... strings) {
-        List<List<Integer>> triangle = new ArrayList();
-        triangle.add(Arrays.asList(1));
-        triangle.add(Arrays.asList(2, 3));
-        System.out.println(minimumTotal(triangle));
-    }
-
+  }
 }
diff --git a/src/test/java/com/fishercoder/_120Test.java b/src/test/java/com/fishercoder/_120Test.java
@@ -0,0 +1,28 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._120;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static junit.framework.Assert.assertEquals;
+
+public class _120Test {
+  private static _120.Solution1 solution1;
+  private static List<List<Integer>> triangle;
+
+  @BeforeClass
+  public static void setup() {
+    solution1 = new _120.Solution1();
+  }
+
+  @Test
+  public void test1() {
+    triangle = new ArrayList();
+    triangle.add(Arrays.asList(1));
+    triangle.add(Arrays.asList(2, 3));
+    assertEquals(3, solution1.minimumTotal(triangle));
+  }
+}
