day 33: 200-number-of-islands, 141-linked-list-cycle

141-linked-list-cycle/driver.cpp

@@ -0,0 +1,16 @@
+#include "soln.hpp"
+
+int main()
+{
+	ListNode n5 = ListNode(5);
+	ListNode n4 = ListNode(4, &n5);
+	ListNode n3 = ListNode(3, &n4);
+	ListNode n2 = ListNode(2, &n3);
+	ListNode n1 = ListNode(1, &n2);
+	n5.next = &n3;
+	bool answer = true;
+
+	Solution soln;
+	cout << "Checked cycle correctly? " << soln.test(&n1, answer) << endl;
+	return 0;
+}

141-linked-list-cycle/soln.cpp

@@ -0,0 +1,19 @@
+#include "soln.hpp"
+
+bool Solution::hasCycle(ListNode *head)
+{
+	ListNode *slow = head, *fast = head;
+	while (fast && fast->next)
+	{
+		slow = slow->next;
+		fast = fast->next->next;
+		if (slow == fast)
+			return true;
+	}
+	return false;
+}
+
+bool Solution::test(ListNode *head, bool answer)
+{
+	return hasCycle(head) == answer;
+}

141-linked-list-cycle/soln.hpp

@@ -0,0 +1,18 @@
+#include <bits/stdc++.h>
+using namespace std;
+/* Singly linked list*/
+struct ListNode
+{
+	int val;
+	ListNode *next;
+	ListNode() : val(0), next(nullptr) {}
+	ListNode(int x) : val(x), next(nullptr) {}
+	ListNode(int x, ListNode *next) : val(x), next(next) {}
+};
+
+class Solution
+{
+public:
+	bool hasCycle(ListNode *head);
+	bool test(ListNode *head, bool answer);
+};

200-number-of-islands/driver.cpp

@@ -0,0 +1,13 @@
+#include "soln.hpp"
+
+int main()
+{
+	vector<vector<char>> grid{{'1', '1', '1', '1', '0'},
+							  {'1', '1', '0', '1', '0'},
+							  {'1', '1', '1', '0', '1'},
+							  {'0', '0', '0', '1', '1'}};
+	int answer = 2;
+	Solution soln;
+	cout << "Found no. of islands correctly? " << soln.test(grid, answer) << endl;
+	return 0;
+}

200-number-of-islands/soln.cpp

@@ -0,0 +1,52 @@
+#include "soln.hpp"
+
+int Solution::numIslands(vector<vector<char>> &grid)
+{
+	// queue<pair<int,int>> current_island{pair<int,int>{0,0}};
+	int islands = 0;
+	for (int i = 0; i < grid.size(); i++)
+	{
+		for (int j = 0; j < grid[0].size(); j++)
+		{
+			// found land
+			if (grid[i][j] == '1')
+			{
+				islands++;
+				grid[i][j] = '0';
+				queue<pair<int, int>> adjs;
+				adjs.push({i, j});
+				while (!adjs.empty())
+				{
+					pair<int, int> adj = adjs.front();
+					adjs.pop();
+					if (adj.first + 1 < grid.size() && grid[adj.first + 1][adj.second] == '1')
+					{
+						grid[adj.first + 1][adj.second] = '0';
+						adjs.push({adj.first + 1, adj.second});
+					}
+					if (adj.first > 0 && grid[adj.first - 1][adj.second] == '1')
+					{
+						grid[adj.first - 1][adj.second] = '0';
+						adjs.push({adj.first - 1, adj.second});
+					}
+					if (adj.second + 1 < grid[0].size() && grid[adj.first][adj.second + 1] == '1')
+					{
+						grid[adj.first][adj.second + 1] = '0';
+						adjs.push({adj.first, adj.second + 1});
+					}
+					if (adj.second > 0 && grid[adj.first][adj.second - 1] == '1')
+					{
+						grid[adj.first][adj.second - 1] = '0';
+						adjs.push({adj.first, adj.second - 1});
+					}
+				}
+			}
+		}
+	}
+	return islands;
+}
+
+bool Solution::test(vector<vector<char>> &grid, int answer)
+{
+	return numIslands(grid) == answer;
+}

200-number-of-islands/soln.hpp

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