day 23: 704-binary-search, 347-top-k-frequent-elements

347-top-k-frequent-elements/driver.cpp

@@ -0,0 +1,10 @@
+#include "soln.hpp"
+
+int main()
+{
+	vector<int> nums{1, 1, 1, 2, 2, 3}, answer{1, 2};
+	int k = 2;
+	Solution soln;
+	cout << "Found top frequent elements correctly? " << soln.test(nums, k, answer) << endl;
+	return 0;
+}

347-top-k-frequent-elements/soln.cpp

@@ -0,0 +1,33 @@
+#include "soln.hpp"
+
+vector<int> Solution::topKFrequent(vector<int> &nums, int k)
+{
+	// first get counts
+	unordered_map<int, int> counts;
+	for (int num : nums)
+	{
+		counts[num]++;
+	}
+	// make a vector indexed by counts. nums can have max nums.size() unique elements, +1 for 0
+	vector<vector<int>> counts_indexed(nums.size() + 1);
+	for (auto count : counts)
+		counts_indexed[count.second].push_back(count.first);
+
+	// iterate in reverse order to get most frequent elements
+	vector<int> result;
+	for (int i = counts_indexed.size() - 1; i > 0; i--)
+	{
+		for (int j = 0; j < counts_indexed[i].size(); j++)
+		{
+			result.push_back(counts_indexed[i][j]);
+			if (result.size() == k)
+				return result;
+		}
+	}
+	return result;
+}
+
+bool Solution::test(vector<int> &nums, int k, vector<int> &answer)
+{
+	return topKFrequent(nums, k) == answer;
+}

347-top-k-frequent-elements/soln.hpp

@@ -0,0 +1,8 @@
+#include <bits/stdc++.h>
+using namespace std;
+class Solution
+{
+public:
+	vector<int> topKFrequent(vector<int> &nums, int k);
+	bool test(vector<int> &nums, int k, vector<int> &answer);
+};

704-binary-search/driver.cpp

@@ -0,0 +1,10 @@
+#include "soln.hpp"
+
+int main()
+{
+	vector<int> nums{-1, 0, 3, 5, 9, 12};
+	int target = 9, answer = 4;
+	Solution soln;
+	cout << "Binary search done correctly ? " << soln.test(nums, target, answer) << endl;
+	return 0;
+}

704-binary-search/soln.cpp

@@ -0,0 +1,25 @@
+#include "soln.hpp"
+
+int Solution::search(vector<int> &nums, int target)
+{
+	int low = 0, high = nums.size() - 1;
+	int mid;
+	while (low != high)
+	{
+		mid = (low + high) / 2;
+		if (nums[mid] == target)
+			return mid;
+		else if (nums[mid] < target)
+			low = mid + 1;
+		else
+			high = mid;
+	}
+	if (nums[low] == target)
+		return low;
+	return -1;
+}
+
+bool Solution::test(vector<int> &nums, int target, int answer)
+{
+	return search(nums, target) == answer;
+}

704-binary-search/soln.hpp

@@ -0,0 +1,8 @@
+#include <bits/stdc++.h>
+using namespace std;
+class Solution
+{
+public:
+	int search(vector<int> &nums, int target);
+	bool test(vector<int> &nums, int target, int answer);
+};