[LEET-515] add 515

fishercoder1534 · fishercoder1534 · commit 9a9d980392cc · 2017-02-12T08:24:59.000-08:00
diff --git a/leetcode-algorithms/README.md b/leetcode-algorithms/README.md
@@ -3,6 +3,7 @@
 ## Algorithms
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|515|[Find Largest Element in Each Row](https://leetcode.com/problems/find-largest-element-in-each-row/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/FindLargestElementinEachRow.java) | O(n) |O(k) | Medium| BFS
 |513|[Find Left Most Element](https://leetcode.com/problems/find-left-most-element/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/FindLeftMostElement.java) | O(n) |O(k) | Medium| BFS
 |504|[Base 7](https://leetcode.com/problems/base-7/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/Base7.java) | O(1) |O(1) | Easy| 
 |501|[Find Mode in Binary Tree](https://leetcode.com/problems/find-mode-in-binary-tree/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/FindModeinBinaryTree.java) | O(n) |O(k) | Easy| Binary Tree
diff --git a/leetcode-algorithms/src/main/java/com/stevesun/solutions/FindLargestElementinEachRow.java b/leetcode-algorithms/src/main/java/com/stevesun/solutions/FindLargestElementinEachRow.java
@@ -0,0 +1,51 @@
+package com.stevesun.solutions;
+
+import com.stevesun.common.classes.TreeNode;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * You need to find the largest value in each row of a binary tree.
+
+ Example:
+ Input:
+
+      1
+     / \
+    3   2
+   / \   \
+  5   3   9
+
+ Output: [1, 3, 9]
+ */
+public class FindLargestElementinEachRow {
+
+    public int[] findValueMostElement(TreeNode root) {
+        Queue<TreeNode> queue = new LinkedList<>();
+        if (root != null) {
+            queue.offer(root);
+            List<Integer> list = new ArrayList<>();
+            while (!queue.isEmpty()) {
+                int max = Integer.MIN_VALUE;
+                int size = queue.size();
+                for (int i = 0; i < size; i++) {
+                    TreeNode curr = queue.poll();
+                    max = Math.max(max, curr.val);
+                    if (curr.left != null) queue.offer(curr.left);
+                    if (curr.right != null) queue.offer(curr.right);
+                }
+                list.add(max);
+            }
+            int[] result = new int[list.size()];
+            for (int i = 0; i < list.size(); i++) {
+                result[i] = list.get(i);
+            }
+            return result;
+        } else {
+            return new int[]{};
+        }
+    }
+}
diff --git a/leetcode-algorithms/src/test/java/com/stevesun/FindLargestElementinEachRowTest.java b/leetcode-algorithms/src/test/java/com/stevesun/FindLargestElementinEachRowTest.java
@@ -0,0 +1,47 @@
+package com.stevesun;
+
+import com.stevesun.common.classes.TreeNode;
+import com.stevesun.solutions.FindLargestElementinEachRow;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class FindLargestElementinEachRowTest {
+    private static FindLargestElementinEachRow test;
+    private static int[] expected;
+    private static int[] actual;
+    private static TreeNode root;
+
+    @BeforeClass
+    public static void setup(){
+        test = new FindLargestElementinEachRow();
+    }
+
+    @Before
+    public void setupForEachTest(){
+        expected = new int[]{};
+        actual = new int[]{};
+        root = new TreeNode(0);
+    }
+
+    @Test
+    public void test1(){
+        TreeNode root = new TreeNode(1);
+        root.left = new TreeNode(3);
+        root.right= new TreeNode(2);
+        expected = new int[]{1, 3};
+        actual = test.findValueMostElement(root);
+        assertArrayEquals(expected, actual);
+
+    }
+
+    @Test
+    public void test2(){
+        expected = new int[]{};
+        actual = test.findValueMostElement(null);
+        assertArrayEquals(expected, actual);
+
+    }
+}
