day 12: 62-unique-paths

62-unique-paths/driver.cpp

@@ -0,0 +1,10 @@
+#include "soln.hpp"
+
+int main()
+{
+	int m = 3, n = 7;
+	int answer = 28;
+	Solution soln;
+	cout << "Found no. of paths correctly? " << soln.test(m, n, answer) << endl;
+	return 0;
+}

62-unique-paths/soln.cpp

@@ -0,0 +1,34 @@
+#include "soln.hpp"
+
+int Solution::uniquePaths(int m, int n)
+{
+	int grid[m][n];
+	// initial condition
+	grid[0][0] = 1;
+	// first row all else 1s: only right moves
+	for (int i = 1; i < n; i++)
+	{
+		grid[0][i] = 1;
+	}
+
+	// first column all 1s: only down moves
+	for (int j = 1; j < m; j++)
+	{
+		grid[j][0] = 1;
+	}
+
+	// no. of paths to a cell = sum of no. of paths to left and top cells
+	for (int i = 1; i < m; i++)
+	{
+		for (int j = 1; j < n; j++)
+		{
+			grid[i][j] = grid[i - 1][j] + grid[i][j - 1];
+		}
+	}
+	return grid[m - 1][n - 1];
+}
+
+bool Solution::test(int m, int n, int answer)
+{
+	return uniquePaths(m, n) == answer;
+}

62-unique-paths/soln.hpp

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