task_01

lesson3/heap.cpp

@@ -0,0 +1,19 @@
+#include <vector>
+//#include <priority_queue>
+
+// left child: 2*i + 1;
+// right child: 2*i + 2;
+// parent: [(i-1)/2];
+
+struct Heap {
+  Heap() : size{0}, values{} {}
+
+  void sift_up(int i);
+  void sift_down(int i);
+  void append(int x);
+
+  std::vector<int> values;
+  int size;
+};
+
+void Heap::sift_up(int i) {}

lesson3/sorting_algorithms.cpp

@@ -0,0 +1,21 @@
+#include <vector>
+
+// bubble_sort: O*(n^2), O(n^2)
+// bogo_sort: O*(n!), O(+inf)
+// insertion_sort: O*(n^2), O(n^2)
+// selection_sort: O*(n^2), O(n^2)
+// merge_sort (top_down/bottom_up): O*(nlogn), O(nlogn)
+// quick_sort: O*(nlogn), (O(n^2) - ineffective, O(nlogn) - effective)
+
+// qsort [] = []
+// qsort(x : xs) = qsort(filter(<x) xs) ++ [x] (filter(=x) xs) ++
+// qsort(filter(>x) xs)
+
+void bubble_sort(std::vector<int>& v) {}
+
+void td_merge_sort(std::vector<int>& v) {
+  for (int l = 1; l < v.size(); l++) {
+    for (int i = 0; i + l < v.size(); i += 2 * l) {
+    }
+  }
+}

sandbox/template/src/commit_message.txt

@@ -0,0 +1 @@
+if you see this it means that the commit worked

sandbox/template/src/main.cpp

@@ -1,3 +1,6 @@
 #include <iostream>
 
-int main() { return 0; }
+int main() {
+  std::cout << "Hello world!";
+  return 0;
+}

task_01/src/main.cpp

@@ -1,3 +1,22 @@
 #include <iostream>
 
-int main() { return 0; }
+#include "solution.h"
+
+int main() {
+  int sum, arr_size, t;
+  std::vector<int> input_vector;
+  std::unordered_map<int, int> indices_map;  // keeps array numbers as keys and
+                                             // indices as values behind keys
+
+  std::cin >> sum >> arr_size;
+
+  for (int i = 0; i < arr_size; i++) {
+    std::cin >> t;
+    input_vector.push_back(t);
+  }
+
+  std::pair<int, int> sol = solution(sum, input_vector);
+  std::cout << sol.first << ' ' << sol.second;
+
+  return 0;
+}

task_01/src/solution.h

@@ -0,0 +1,44 @@
+#include <unordered_map>
+#include <vector>
+
+/*
+
+Output - indices of two numbers, which sum is equal to needed number, if there's
+no such numbers, the output is "-1 -1"
+
+Input:
+
+10
+10
+-2 2 3 3 5 8 11 13 14 15
+
+Output:
+
+1 5
+
+*/
+
+// Solution below has a time complexity of O(n) and memory complexity of O(n)
+
+std::pair<int, int> solution(int sum, std::vector<int> v) {
+  bool flag = false;  // in case there are no such numbers
+  std::unordered_map<int, int> indices_map;  // keeps array numbers as keys and
+                                             // indices as values behind keys
+
+  for (int i = 0; i < v.size(); i++) {
+    if (indices_map.find(sum - v[i]) !=
+        indices_map
+            .end()) {  // if key "number - t" exists, we have found the solution
+      return {indices_map[sum - v[i]], i};
+      flag = true;
+      break;
+    }
+
+    if (indices_map.find(v[i]) == indices_map.end())
+      indices_map[v[i]] =
+          i;  // We only add keys that weren't in the map before (that
+              // way we get the least possible sum of i and j)
+  }
+
+  if (!flag) return {-1, -1};
+}

task_01/src/test.cpp

@@ -1,8 +1,40 @@
 
 #include <gtest/gtest.h>
 
+#include "solution.h"
 #include "topology_sort.hpp"
 
-TEST(TopologySort, Simple) {
-  ASSERT_EQ(1, 1);  // Stack []
-}
+TEST(solution, simple) {
+  std::vector<int> v1 = {-2, 2, 3, 3, 5, 9, 11, 13, 14, 15};
+  std::pair<int, int> p1 = {-1, -1};
+  ASSERT_EQ(p1, solution(10, v1));
+
+  std::vector<int> v2 = {-2, 2, 3, 3, 5, 8, 11, 13, 14, 15};
+  std::pair<int, int> p2 = {1, 5};
+  ASSERT_EQ(p2, solution(10, v2));
+
+  std::vector<int> v3 = {};
+  std::pair<int, int> p3 = {-1, -1};
+  ASSERT_EQ(p3, solution(0, v3));
+
+  std::vector<int> v4 = {1};
+  std::pair<int, int> p4 = {-1, -1};
+  ASSERT_EQ(p4, solution(1, v4));
+
+  std::vector<int> v5 = {1, 2};
+  std::pair<int, int> p5 = {0, 1};
+  ASSERT_EQ(p5, solution(3, v5));
+
+  // if there are multiple solutions, the algorithm
+  // will pick the one, in which sum of i and j is the least,
+  // where i and j are indices of numbers, which sum is equal to needed number
+  std::vector<int> v6 = {1, 1, 1, 1, 1, 1, 1, 1, 1};
+  std::pair<int, int> p6 = {0, 1};
+  ASSERT_EQ(p6, solution(2, v6));
+
+  // in case there are multiple solutions in which i+j is the least,
+  // the algorithm will pick the one, in which i is greater
+  std::vector<int> v7 = {1, 2, 1, 1, 4, 5, 1, 1, 1};
+  std::pair<int, int> p7 = {1, 4};
+  ASSERT_EQ(p7, solution(6, v7));
+}