2384. Largest Palindromic Number

Author: orhtej2

CMakeLists.txt

@@ -47,4 +47,5 @@ add_subdirectory( kth-largest-element-in-a-stream )
 add_subdirectory( kth-largest-element-in-a-array )
 add_subdirectory( wiggle-sort-ii )
 add_subdirectory( longest-palindrome )
-add_subdirectory( longest-palindrome-by-concatenating-two-letter-words )
+add_subdirectory( longest-palindrome-by-concatenating-two-letter-words )
+add_subdirectory( largest-palindromic-number )

largest-palindromic-number/CMakeLists.txt

@@ -0,0 +1,19 @@
+project(largest_palindromic_number)
+
+add_executable(
+  largest_palindromic_number_runner
+  runner.cpp
+)
+
+add_executable(
+  largest_palindromic_number_tests
+  tests.cpp
+)
+
+target_link_libraries(
+  largest_palindromic_number_tests
+  GTest::gtest_main
+)
+
+
+gtest_discover_tests(largest_palindromic_number_tests)

largest-palindromic-number/README.md

@@ -0,0 +1,3 @@
+# 2384. Largest Palindromic Number
+
+[LeetCode link](https://leetcode.com/problems/largest-palindromic-number/)

largest-palindromic-number/runner.cpp

@@ -0,0 +1,13 @@
+#include <iostream>
+#include <string>
+
+#include "solution.hpp"
+
+int main()
+{
+    const std::string input = "112";
+    Solution s;
+    std::cout << "\"" << input << "\": " << s.largestPalindromic(input) << std::endl;
+
+    return 0;
+}

largest-palindromic-number/solution.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <algorithm>
+#include <cstring>
+#include <string>
+
+class Solution {
+public:
+  std::string largestPalindromic(const std::string& s) {
+    int counts[10];
+    std::memset(counts, 0, sizeof(int) * 10);
+    for (auto c : s) {
+      counts[c - '0']++;
+    }
+
+    std::string result;
+    bool nonzero = false;
+    for (int i = 9; i > 0 || (i == 0 && nonzero); --i) {
+      while (counts[i] > 1) {
+        result += ('0' + i);
+        counts[i] -= 2;
+        nonzero = true;
+      }
+    }
+    std::string mid;
+    for (int i = 9; i >= 0; --i) {
+      if (counts[i] != 0) {
+        mid = '0' + i;
+        break;
+      }
+    }
+
+    result += mid + std::string(result.rbegin(), result.rend());
+    return result;
+  }
+};

largest-palindromic-number/tests.cpp

@@ -0,0 +1,34 @@
+#include <string>
+#include <utility>
+
+#include <gtest/gtest.h>
+
+#include "solution.hpp"
+
+class LargestPalindromicNumberTest : public ::testing::TestWithParam<std::pair<std::string, std::string>> {
+protected:
+    Solution solution;
+};
+
+TEST_P(LargestPalindromicNumberTest, CheckSolution) {
+    std::string input = std::get<0>(GetParam());
+    std::string expected = std::get<1>(GetParam());
+
+    auto actual = solution.largestPalindromic(input);
+
+    EXPECT_EQ(expected, actual);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+  LargestPalindromicNumberTests,
+  LargestPalindromicNumberTest,
+        ::testing::Values(
+          std::make_pair<std::string, std::string>("1", "1"),
+          std::make_pair<std::string, std::string>("12", "2"),
+          std::make_pair<std::string, std::string>("112", "121"),
+          std::make_pair<std::string, std::string>("1122", "2112"),
+          std::make_pair<std::string, std::string>("100", "1"),
+          std::make_pair<std::string, std::string>("00", "0"),
+          std::make_pair<std::string, std::string>("110", "101")
+          )
+);