Design Pattern 3: Two Pointers | Problem: Squares of a Sorted Array

3_squares_of_a_sorted_array.cpp

@@ -0,0 +1,47 @@
+/* Problem source: https://leetcode.com/problems/squares-of-a-sorted-array/
+ */
+
+#include <iostream>
+#include <vector>
+
+template <typename T> inline T absolute(T num) {
+  return num > -num ? num : -num;
+}
+
+template <typename T> inline T square(T num) { return num * num; }
+
+template <typename T>
+std::vector<T> &solution(const std::vector<T> &sorted_input) {
+  std::vector<T> *result = new std::vector<T>(sorted_input.size());
+  std::vector<T> &sorted_output = *result;
+  unsigned long long p1 = 0, p2 = 1;
+  while (p2 < sorted_input.size()) {
+    if (absolute(sorted_input[p2]) <= absolute(sorted_input[p1]))
+      p1 = p2++;
+    else
+      break;
+  }
+
+  //   std::cout << sorted_input[p1] << ", " << sorted_input[p2] << "\n";
+
+  unsigned long long output_p = 0;
+  while (p1 < p2 && p2 < sorted_input.size()) {
+    if (absolute(sorted_input[p1]) < absolute(sorted_input[p2]))
+      sorted_output[output_p++] = (square(sorted_input[p1--]));
+    else
+      sorted_output[output_p++] = square(sorted_input[p2++]);
+  }
+  while (p1 < p2)
+    sorted_output[output_p++] = square(sorted_input[p1--]);
+  while (p2 < sorted_input.size())
+    sorted_output[output_p++] = square(sorted_input[p2++]);
+  return sorted_output;
+}
+
+int main() {
+  std::vector<int> &result = solution(std::vector{-4, -1, 0, 3, 10});
+  for (const int num : result)
+    std::cout << num << ", ";
+  std::cout << std::endl;
+  delete &result;
+}

CMakeLists.txt

@@ -10,3 +10,5 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall  -Wextra -Werror -g")
 add_executable(1_longest_substring_with_k_distinct_characters 1_longest_substring_with_k_distinct_characters.cpp)
 
 add_executable(2_num_of_islands 2_num_of_islands.cpp)
+
+add_executable(3_squares_of_a_sorted_array 3_squares_of_a_sorted_array.cpp)