feature: dp house robber 2 solution added

Author: Debashis08

include/0005_DynamicProgramming/0006_HouseRobber2.h

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+#pragma once
+#include<vector>
+using namespace std;
+
+/*
+Pattern 1
+Linear Recurrence
+
+Description
+You are given an array arr[] which represents houses arranged in a circle, where each house has a certain value. A thief aims to maximize the total stolen value without robbing two adjacent houses.
+Determine the maximum amount the thief can steal.
+
+Note: Since the houses are in a circle, the first and last houses are also considered adjacent.
+
+*/
+
+namespace HouseRobber2
+{
+	class DynamicProgramming
+	{
+	private:
+		int MaxLootRecursive(size_t house, vector<int>& houseValues);
+		int MaxLootDp(size_t firstHouse, size_t lastHouse, vector<int>& houseValues);
+	public:
+		int RecursiveMaximumLoot(vector<int>& houseValues);
+		int DpMaximumLoot(vector<int>& houseValues);
+	};
+}

source/0005_DynamicProgramming/0006_HouseRobber2.cc

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+#include "../../include/0005_DynamicProgramming/0006_HouseRobber2.h"
+
+namespace HouseRobber2
+{
+	int DynamicProgramming::MaxLootRecursive(size_t house, vector<int>& houseValues)
+	{
+		if (house <= 0)
+		{
+			return 0;
+		}
+
+		if (house == 1)
+		{
+			return houseValues[0];
+		}
+
+		int pickCurrentHouse = houseValues[house - 1] + this->MaxLootRecursive(house - 2, houseValues);
+		int dropCurrentHouse = this->MaxLootRecursive(house - 1, houseValues);
+
+		return max(pickCurrentHouse, dropCurrentHouse);
+	}
+
+	int DynamicProgramming::MaxLootDp(size_t firstHouse, size_t lastHouse, vector<int>& houseValues)
+	{
+		int totalNumberOfHouses = lastHouse - firstHouse + 1;
+
+		if (totalNumberOfHouses == 0)
+		{
+			return 0;
+		}
+
+		if (totalNumberOfHouses == 1)
+		{
+			return houseValues[firstHouse];
+		}
+
+		vector<int> dp(totalNumberOfHouses, 0);
+
+		dp[0] = houseValues[firstHouse];
+		dp[1] = max(houseValues[firstHouse], houseValues[firstHouse + 1]);
+
+		for (size_t i = 2; i < totalNumberOfHouses; i++)
+		{
+			dp[i] = max(houseValues[firstHouse + i] + dp[i - 2], dp[i - 1]);
+		}
+
+		return dp[totalNumberOfHouses - 1];
+	}
+
+	int DynamicProgramming::RecursiveMaximumLoot(vector<int>& houseValues)
+	{
+		if (houseValues.size() == 0)
+		{
+			return 0;
+		}
+
+		if (houseValues.size() == 1)
+		{
+			return houseValues[0];
+		}
+
+		size_t totalNumberOfHouses = houseValues.size()-1;
+
+		// Case 1: Exclude last house.
+		vector<int> pickFirstHouse(houseValues.begin(), houseValues.end() - 1);
+
+		// Case 2: Exlcude first house.
+		vector<int> pickLastHouse(houseValues.begin() + 1, houseValues.end());
+
+		return max(this->MaxLootRecursive(totalNumberOfHouses, pickFirstHouse), this->MaxLootRecursive(totalNumberOfHouses, pickLastHouse));
+	}
+
+	int DynamicProgramming::DpMaximumLoot(vector<int>& houseValues)
+	{
+		size_t totalNumberOfHouses = houseValues.size();
+
+		if (totalNumberOfHouses == 0)
+		{
+			return 0;
+		}
+
+		if (totalNumberOfHouses == 1)
+		{
+			return houseValues[0];
+		}
+
+		// Case 1: Exclude last house.
+		int pickFirstHouse = this->MaxLootDp(0, totalNumberOfHouses - 2, houseValues);
+
+		// Case 2: Exlcude first house.
+		int pickLastHouse = this->MaxLootDp(1, totalNumberOfHouses - 1, houseValues);
+
+		return max(pickFirstHouse, pickLastHouse);
+	}
+}

test/0005_DynamicProgramming/0006_HouseRobber2Test.cc

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+#include<gtest/gtest.h>
+#include "../../include/0005_DynamicProgramming/0006_HouseRobber2.h"
+
+namespace HouseRobber2
+{
+	TEST(HouseRobber2, RecursionTest01)
+	{
+		// Arrange
+		DynamicProgramming dp;
+		vector<int> houseValues = { 2, 2, 3, 1, 2 };
+		int expectedMaximumLoot = 5;
+
+		// Act
+		int actualMaximumLoot = dp.RecursiveMaximumLoot(houseValues);
+
+		// Assert
+		ASSERT_EQ(expectedMaximumLoot, actualMaximumLoot);
+	}
+
+	TEST(HouseRobber2, DpTest01)
+	{
+		// Arrange
+		DynamicProgramming dp;
+		vector<int> houseValues = { 2, 2, 3, 1, 2 };
+		int expectedMaximumLoot = 5;
+
+		// Act
+		int actualMaximumLoot = dp.DpMaximumLoot(houseValues);
+
+		// Assert
+		ASSERT_EQ(expectedMaximumLoot, actualMaximumLoot);
+	}
+
+	TEST(HouseRobber2, DpTest02)
+	{
+		// Arrange
+		DynamicProgramming dp;
+		vector<int> houseValues = { 9, 1, 8, 2 };
+		int expectedMaximumLoot = 17;
+
+		// Act
+		int actualMaximumLoot = dp.DpMaximumLoot(houseValues);
+
+		// Assert
+		ASSERT_EQ(expectedMaximumLoot, actualMaximumLoot);
+	}
+
+}