[Hacker Rank]: Warmup: Plus Minus. Solved ✅.

docs/hackerrank/warmup/plus_minus.md

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+# [Plus Minus](https://www.hackerrank.com/challenges/plus-minus)
+
+Difficulty: #easy
+Category: #warmup
+
+Given an array of integers, calculate the ratios of its elements
+that are positive, negative, and zero. Print the decimal value of
+each fraction on a new line with 6 places after the decimal.
+
+**Note**: This challenge introduces precision problems.
+The test cases are scaled to six decimal places, though answers
+with absolute error of up to $ 10^{-4} $ are acceptable.
+
+## Example
+
+$ arr = [1, 1, 0, -1, -1] $
+
+There are $ n = 5 $ elements, two positive, two negative and one zero.
+Their ratios are $ 2/5 = 0.400000 $, $ 2/5 = 0.400000 $ and $ 1/5 = 0.200000 $.
+Results are printed as:
+
+```text
+0.400000
+0.400000
+0.200000
+```
+
+## Function Description
+
+Complete the plusMinus function in the editor below.
+plusMinus has the following parameter(s):
+
+- int arr[n]: an array of integers
+
+## Print
+
+Print the ratios of positive, negative and zero values in the array.
+Each value should be printed on a separate line with $ 6 $ digits after
+the decimal. The function should not return a value.
+
+## Input Format
+
+The first line contains an integer, `n`, the size of the array.
+The second line contains `n` space-separated integers that describe `arr[n]`.
+
+## Constraints
+
+$ 0 < n \leq 100 $ \
+$ -100 \leq arr[i] \leq 100 $
+
+## Output Format
+
+**Print** the following  lines, each to  decimals:
+
+1. proportion of positive values
+2. proportion of negative values
+3. proportion of zeros
+
+## Sample Input
+
+```text
+STDIN           Function
+-----           --------
+6               arr[] size n = 6
+-4 3 -9 0 4 1   arr = [-4, 3, -9, 0, 4, 1]
+```
+
+## Sample Output
+
+```text
+0.500000
+0.333333
+0.166667
+```
+
+## Explanation
+
+There are $ 3 $ positive numbers, negative numbers, and $ 1 $ zero in the array.
+The proportions of occurrence are positive: $ 3/6 = 0.500000 $,
+negative: $ 2/6 = 0.333333 $ and zeros: $ 1/6 = 0.166667 $.

src/lib/exercises/include/exercises/hackerrank/warmup/plus_minus.hpp

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+#include <string>
+#include <vector>
+#pragma once
+
+namespace hackerrank::warmup {
+std::vector<std::string> plusMinusCalculate(const std::vector<int> &arr);
+void plusMinus(const std::vector<int> &arr);
+} // namespace hackerrank::warmup

src/lib/exercises/src/hackerrank/warmup/plus_minus.cpp

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+#include <exercises/hackerrank/warmup/plus_minus.hpp>
+
+/**
+ * @link Problem definition [[docs/hackerrank/warmup/plus_minus.md]]
+ */
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+#define BUFFER_MAX_SIZE 100
+
+std::string format_result(double number) {
+  char buffer[BUFFER_MAX_SIZE];
+
+  snprintf(buffer, BUFFER_MAX_SIZE, "%0.6lf", number);
+  std::string formatted = buffer;
+
+  return formatted;
+}
+
+namespace hackerrank::warmup {
+std::vector<std::string> plusMinusCalculate(const std::vector<int> &arr) {
+  unsigned long positives = 0;
+  int negatives = 0;
+  int zeros = 0;
+
+  for (const int &value : arr) {
+    if (value > 0) {
+      positives += 1;
+    }
+    if (value < 0) {
+      negatives += 1;
+    }
+    if (value == 0) {
+      zeros += 1;
+    }
+  }
+
+  std::vector<double> results = {
+      static_cast<double>(positives) / static_cast<double>(arr.size()),
+      static_cast<double>(negatives) / static_cast<double>(arr.size()),
+      static_cast<double>(zeros) / static_cast<double>(arr.size())};
+
+  std::vector<std::string> answer = {};
+
+  for (double tmp : results) {
+    std::string formatted = format_result(tmp);
+    answer.emplace_back(formatted);
+  }
+
+  return answer;
+}
+
+void plusMinus(const std::vector<int> &arr) {
+  std::vector<std::string> output = plusMinusCalculate(arr);
+
+  for (const std::string &line : output) {
+    std::cout << line << std::endl;
+  }
+}
+} // namespace hackerrank::warmup

src/tests/unit/lib/hackerrank/warmup/plus_minus.test.cpp

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+#include <catch2/catch_test_macros.hpp>
+
+#include <exercises/hackerrank/warmup/plus_minus.hpp>
+#include <iostream>
+#include <stdexcept>
+#include <vector>
+
+#include <filesystem>
+#include <fstream>
+#include <nlohmann/json.hpp>
+using json = nlohmann::json;
+
+TEST_CASE("plusMinus JSON Test Cases", "[warmup]") {
+  std::filesystem::path cwd = std::filesystem::current_path();
+  std::string path =
+      cwd.string() + "/unit/lib/hackerrank/warmup/plus_minus.testcases.json";
+
+  INFO("plusMinus JSON test cases FILE: " << path);
+
+  std::ifstream f(path);
+  json data = json::parse(f);
+
+  for (auto testcase : data) {
+    hackerrank::warmup::plusMinus(testcase["input"]);
+    std::vector<std::string> result =
+        hackerrank::warmup::plusMinusCalculate(testcase["input"]);
+    CHECK(result == testcase["expected"]);
+  }
+}

src/tests/unit/lib/hackerrank/warmup/plus_minus.testcases.json

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+[
+  {
+    "title": "test case 0",
+    "input": [-4, 3, -9, 0, 4, 1],
+    "expected": ["0.500000", "0.333333", "0.166667"]
+  }
+]