TheAlgorithms-C-Plus-Plus/dynamic_programming/house_robber.cpp

/**
 * @file
 * @brief Implementation of [House Robber Problem] algorithm
 * @details
 * Solution of House robber problem uses a dynamic programming concept that works in \f$O(n)\f$ time and works in \f$O(1)\f$ space.
 */

#include <cassert>    /// for assert
#include <iostream>   /// for io operations
#include <vector>     /// for std::vector

/**
 * @namespace dynamic_programming
 * @brief House robber algorithm
 */
namespace dynamic_programming {
/**
 * @namespace house_robber
 * @brief Functions for House Robber algorithm
 */
namespace house_robber {
/**
 * @brief The main function implements house robber algorithm using dynamic programming
 * @param money array containing money in the ith house
 * @param n size of array
 * @returns maximum amount of money that can be robbed
 */
std::uint64_t houseRobber(const std::vector<int> &money, int n) {

    if (n == 0) { // if there is no house
      return 0;
    }
    if (n == 1) { // if there is only one house
      return money[0];
    }
    if (n == 2) { // if there are two houses, one with the maximum amount of money will be robbed
      if (money[0] > money[1]) {
        return money[0];
      }
      return money[1];
    }
    int max_value; // contains maximum stolen value at the end
    int value1 = money[0];
    int value2;
    if (money[0] > money[1]) {
        value2 = money[0];
    }
    else{
        value2 = money[1];
    }
    for (int i=2; i<n; i++) {
       if (money[i]+value1 > value2) {
          max_value = (money[i]+value1);
       }
       else{
          max_value = (value2);
       }
       value1 = value2;
       value2 = max_value;
    }
 
    return max_value;
}
}  // namespace house_robber
}  // namespace dynamic_programming

/**
 * @brief Test implementations
 * @returns void
 */
static void test() {
    // [1, 2, 3, 1] return 4
    std::vector<int> array1 = {1, 2, 3, 1};
    std::cout << "Test 1... ";
    assert(dynamic_programming::house_robber::houseRobber(array1,array1.size())==4); // here the two non-adjacent houses that are robbed are first and third with total sum money as 4
    std::cout << "passed" << std::endl;

    // [6, 7, 1, 3, 8, 2, 4] return 19
    std::vector<int> array2 = {6, 7, 1, 3, 8, 2, 4};
    std::cout << "Test 2... ";
    assert(dynamic_programming::house_robber::houseRobber(array2,array2.size())==19); // here the four non-adjacent houses that are robbed are first, third, fifth and seventh with total sum money as 19
    std::cout << "passed" << std::endl;

    // [] return 0
    std::vector<int> array3 = {};
    std::cout << "Test 3... ";
    assert(dynamic_programming::house_robber::houseRobber(array3,array3.size())==0); // since there is no house no money can be robbed
    std::cout << "passed" << std::endl;

    // [2,7,9,3,1] return 12
    std::vector<int> array4 = {2,7,9,3,1};
    std::cout << "Test 4... ";
    assert(dynamic_programming::house_robber::houseRobber(array4,array4.size())==12); // here the three non-adjacent houses that are robbed are first, third and fifth with total sum money as 12
    std::cout << "passed" << std::endl;
}

/**
 * @brief Main function
 * @returns 0 on exit
 */
int main() {
    test();  // execute the test
    return 0;
}