add: 220530-CN [cpp]

cpp/2205/220530-CN.cpp

@@ -0,0 +1,28 @@
+struct TreeNode {
+	int val;
+	TreeNode* left;
+	TreeNode* right;
+	explicit TreeNode(int x, TreeNode* left = nullptr, TreeNode* right = nullptr) : val(x), left(left), right(right) {}
+};
+
+/**
+ * 1022. Sum of Root To Leaf Binary Numbers
+ * You are given the root of a binary tree where each node has a value 0 or 1. Each root-to-leaf path represents a binary number starting with the most significant bit.
+ * For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.
+ * For all leaves in the tree, consider the numbers represented by the path from the root to that leaf. Return the sum of these numbers.
+ * The test cases are generated so that the answer fits in a 32-bits integer.
+ *
+ * Refer: 220111.cpp
+ */
+
+class Solution {
+public:
+	int sumRootToLeaf(TreeNode* root, int sum = 0) {
+		if (!root)
+			return 0;
+		const int ans = (sum << 1) + root->val;
+		if (!root->left && !root->right)
+			return ans;
+		return sumRootToLeaf(root->left, ans) + sumRootToLeaf(root->right, ans);
+	}
+};