404:左叶子之和

src/main/java/leetcode/editor/cn/SumOfLeftLeaves.java

@@ -0,0 +1,67 @@
+//计算给定二叉树的所有左叶子之和。 
+//
+// 示例： 
+//
+// 
+//    3
+//   / \
+//  9  20
+//    /  \
+//   15   7
+//
+//在这个二叉树中，有两个左叶子，分别是 9 和 15，所以返回 24 
+//
+// 
+// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 
+// 👍 328 👎 0
+
+package leetcode.editor.cn;
+
+import com.code.leet.entiy.TreeNode;
+
+//404:左叶子之和
+class SumOfLeftLeaves {
+    public static void main(String[] args) {
+        //测试代码
+        Solution solution = new SumOfLeftLeaves().new Solution();
+    }
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+
+    /**
+     * Definition for a binary tree node.
+     * public class TreeNode {
+     * int val;
+     * TreeNode left;
+     * TreeNode right;
+     * TreeNode() {}
+     * TreeNode(int val) { this.val = val; }
+     * TreeNode(int val, TreeNode left, TreeNode right) {
+     * this.val = val;
+     * this.left = left;
+     * this.right = right;
+     * }
+     * }
+     */
+    class Solution {
+
+        public int sumOfLeftLeaves(TreeNode root) {
+            if (root == null) {
+                return 0;
+            }
+            int sum = 0;
+            if (root.left != null) {
+                if (root.left.left == null && root.left.right == null) {
+                    sum += root.left.val;
+                }
+                sum += sumOfLeftLeaves(root.left);
+            }
+            if (root.right != null) {
+                sum += sumOfLeftLeaves(root.right);
+            }
+            return sum;
+        }
+    }
+//leetcode submit region end(Prohibit modification and deletion)
+
+}

src/main/java/leetcode/editor/cn/SumOfLeftLeaves.md

@@ -0,0 +1,15 @@
+<p>计算给定二叉树的所有左叶子之和。</p>
+
+<p><strong>示例：</strong></p>
+
+<pre>
+    3
+   / \
+  9  20
+    /  \
+   15   7
+
+在这个二叉树中，有两个左叶子，分别是 9 和 15，所以返回 24</pre>
+
+<p>&nbsp;</p>
+<div><div>Related Topics</div><div><li>树</li><li>深度优先搜索</li><li>广度优先搜索</li><li>二叉树</li></div></div>\n<div><li>👍 328</li><li>👎 0</li></div>