cpp: add “1457. Pseudo-Palindromic Paths in a Binary Tree”

Signed-off-by: Matej Focko <me@mfocko.xyz>

cpp/pseudo-palindromic-paths-in-a-binary-tree.cpp

@@ -0,0 +1,59 @@
+#include <array>
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
+ * right(right) {}
+ * };
+ */
+class Solution {
+    static auto leaf(TreeNode *node) -> bool {
+        return node != nullptr &&
+               (node->left == nullptr && node->right == nullptr);
+    }
+
+    static auto palindrome(const std::array<int, 10> &counters) -> bool {
+        int odd = 0;
+
+        for (int d = 1; d < 10; ++d) {
+            if (counters[d] % 2 == 1) {
+                ++odd;
+            }
+        }
+
+        return odd <= 1;
+    }
+
+    static auto pseudoPalindromicPaths(TreeNode *node,
+                                       std::array<int, 10> &counters) -> int {
+        if (node == nullptr) {
+            return counters[0];
+        }
+
+        ++counters[node->val];
+
+        if (leaf(node) && palindrome(counters)) {
+            ++counters[0];
+        }
+
+        pseudoPalindromicPaths(node->left, counters);
+        pseudoPalindromicPaths(node->right, counters);
+
+        --counters[node->val];
+        return counters[0];
+    }
+
+  public:
+    int pseudoPalindromicPaths(TreeNode *root) {
+        std::array<int, 10> counters;
+        counters.fill(0);
+
+        return pseudoPalindromicPaths(root, counters);
+    }
+};