1497-check-if-array-pairs-are-divisible-by-k

1497-check-if-array-pairs-are-divisible-by-k/driver.cpp

@@ -0,0 +1,12 @@
+#include "soln.hpp"
+
+int main()
+{
+	Solution soln;
+	vector<int> arr{1, 2, 3, 4, 5, 6};
+	int k = 10;
+	bool answer = false;
+	cout << "Checked pairings correctly? " << endl;
+	cout << soln.test(arr, k, answer) << endl;
+	return 0;
+}

1497-check-if-array-pairs-are-divisible-by-k/soln.cpp

@@ -0,0 +1,77 @@
+#include "soln.hpp"
+
+bool Solution::DEBUG = true;
+
+bool Solution::canArrange(vector<int> &arr, int k)
+{
+	// vector<int> result = vector<int>();
+	// for (int num = 0; num < arr.size(); num++)
+	// {
+	// 	bool found_pair = false;
+	// 	for (int existing = 0; existing < result.size(); existing++)
+	// 	{
+	// 		if ((arr[num] + result[existing]) % k == 0)
+	// 		{
+	// 			found_pair = true;
+	// 			dbg("pop", result[existing]);
+	// 			result.erase(find(result.begin(), result.end(), result[existing]));
+	// 			break;
+	// 		}
+	// 	}
+	// 	if (!found_pair)
+	// 	{
+	// 		result.emplace_back(arr[num]);
+	// 		dbg("insert", arr[num]);
+	// 	}
+	// }
+	// return !(result.size() > 0);
+
+	vector<int> rems;
+	int zeros = 0;
+	for (int i = 0; i < arr.size(); i++)
+	{
+		if (arr[i] % k == 0)
+		{
+			zeros++;
+		}
+		else if (arr[i] % k < 0)
+		{
+			rems.emplace_back((arr[i] % k) + k);
+		}
+		else
+		{
+			rems.emplace_back(arr[i] % k);
+		}
+	}
+	if (zeros % 2)
+	{
+		return false;
+	}
+	unordered_map<int, int> result;
+	for (int i = 0; i < rems.size(); i++)
+	{
+		if (result.find(k - rems[i]) != result.end() && result[k - rems[i]] > 0)
+		{
+			result[k - rems[i]]--;
+			dbg("pop", k - rems[i]);
+		}
+		else
+		{
+			result[rems[i]] = result[rems[i]] + 1;
+			dbg("insert", rems[i]);
+		}
+	}
+	for (auto it = result.begin(); it != result.end(); it++)
+	{
+		if (it->second > 0)
+		{
+			return false;
+		}
+	}
+	return true;
+}
+
+bool Solution::test(vector<int> &arr, int k, bool answer)
+{
+	return canArrange(arr, k) == answer;
+}

1497-check-if-array-pairs-are-divisible-by-k/soln.hpp

@@ -0,0 +1,22 @@
+#include <bits/stdc++.h>
+using namespace std;
+class Solution
+{
+public:
+	static bool DEBUG;
+
+	template <typename... Args>
+	void dbg(Args &&...args)
+	{
+		if (DEBUG)
+		{
+			const char *sep = " ";
+			const char *label = "[DEBUG]";
+			cout << label;
+			(((cout << sep << args), sep = sep), ...);
+			cout << endl;
+		}
+	}
+	bool canArrange(vector<int> &arr, int k);
+	bool test(vector<int> &arr, int k, bool answer);
+};

1497-check-if-array-pairs-are-divisible-by-k/soln.py

@@ -0,0 +1,49 @@
+class Solution:
+    def canArrange(self, arr: list[int], k: int) -> bool:
+        # DEBUG = False
+        # dbg_print = lambda *x: print(f"[DEBUG] {x}") if DEBUG else print("", end="")
+
+        # # brute force, TLE
+        # result = []
+        # for num in arr:
+        #     found_pair = False
+        #     for existing in result:
+        #         if (num+existing) % k == 0:
+        #             found_pair = True
+        #             result.remove(existing)
+        #             break
+        #     if not found_pair:
+        #         result.append(num)
+
+        # return not len(result) > 0
+
+        # idea: sum of remainders will be divisible too
+        rems = [x % k for x in arr]
+        # dbg_print("rems", rems)
+        zeros = 0
+        for rem in rems:
+            if rem == 0:
+                zeros += 1
+        if zeros % 2:
+            return False
+        rems[:] = [x for x in rems if x]
+        # dbg_print("rems without zeros", rems)
+
+        result = {}
+        for rem in rems:
+            if k - rem in result.keys() and result[k - rem] > 0:
+                result[k - rem] -= 1
+                # dbg_print("pop", k-rem)
+            else:
+                result[rem] = result.get(rem, 0) + 1
+                # dbg_print("insert", rem)
+        for x in result.keys():
+            if result[x]:
+                return False
+
+        return True
+
+
+if __name__ == "__main__":
+    soln = Solution()
+    print(soln.canArrange([1, 2, 3, 4, 5, 10, 6, 7, 8, 9], 5))

template/soln.cpp

@@ -1,2 +1,3 @@
 #include "soln.hpp"
 
+bool Solution::DEBUG = true;

template/soln.hpp

@@ -3,6 +3,21 @@ using namespace std;
 class Solution
 {
 public:
+	static bool DEBUG;
+
+	template <typename... Args>
+	void dbg(Args &&...args)
+	{
+		if (DEBUG)
+		{
+			const char *sep = " ";
+			const char *label = "[DEBUG]";
+			cout << label;
+			(((cout << sep << args), sep = sep), ...);
+			cout << endl;
+		}
+	}
+
 	
 	bool test(, bool answer);
 };