Largest Number After Digit Swaps by Parity

CMakeLists.txt

@@ -322,6 +322,7 @@ add_task(kth-smallest-element-in-a-bst)
 add_task(largest-3-same-digit-number-in-string)
 add_task(largest-color-value-in-a-directed-graph)
 add_task(largest-local-values-in-a-matrix)
+add_task(largest-number-after-digit-swaps-by-parity)
 add_task(largest-perimeter-triangle)
 add_task(largest-positive-integer-that-exists-with-its-negative)
 add_task(largest-rectangle-in-histogram)

solutions/largest-number-after-digit-swaps-by-parity/CMakeLists.txt

@@ -0,0 +1 @@
+add_catch(test_largest_number_after_digit_swaps_by_parity test.cpp)

solutions/largest-number-after-digit-swaps-by-parity/solution.hpp

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <queue>
+#include <vector>
+
+class Solution {
+public:
+  static int largestInteger(int num) {
+    const auto digits = getDigits(num);
+
+    std::vector<std::priority_queue<int>> heaps(2);
+    for (auto digit : digits) {
+      heaps[digit & 1].push(digit);
+    }
+
+    int ans = 0;
+    for (auto digit : digits) {
+      ans = ans * 10 + heaps[digit & 1].top();
+      heaps[digit & 1].pop();
+    }
+    return ans;
+  }
+
+private:
+  static std::vector<int> getDigits(int n) {
+    std::vector<int> digits;
+    for (int i = n; i; i /= 10) {
+      digits.push_back(i % 10);
+    }
+    std::reverse(digits.begin(), digits.end());
+    return digits;
+  }
+};

solutions/largest-number-after-digit-swaps-by-parity/test.cpp

@@ -0,0 +1,26 @@
+#include <catch.hpp>
+
+#include <solution.hpp>
+
+TEST_CASE("Simple") {
+  struct TestCase {
+    int num;
+    int expected;
+  };
+
+  std::vector<TestCase> test_cases{
+      {
+          .num = 1234,
+          .expected = 3412,
+      },
+      {
+          .num = 65875,
+          .expected = 87655,
+      },
+  };
+
+  for (const auto &[num, expected] : test_cases) {
+    const auto actual = Solution::largestInteger(num);
+    REQUIRE(expected == actual);
+  }
+}