findMaxProduct.cpp

#include <iostream>
#include <vector>
#include <cassert>

using namespace std;

int findMaxProduct(vector<int> &nums) {
  if (nums.empty()) return 0;

  int best;
  int maxProduct, minProduct;
  best = maxProduct = minProduct = nums[0];

  for (unsigned i = 1; i < nums.size(); ++i) {
    int n = nums[i];
    int n_max = n * maxProduct;
    int n_min = n * minProduct;

    maxProduct = max(n, max(n_max, n_min));
    minProduct = min(n, min(n_max, n_min));
    best = max(best, maxProduct);
  }

  return best;
}

vector<int> nums1 {2, -7, 0, 2, 3, 8, -6, 5};
vector<int> nums2 {-2, 0, 3, 5, -7};
vector<int> nums3 {2, -7, 0, 2, 3, 8, -6, 5, -1};
vector<int> nums4 {-1, -2, -3};
vector<int> nums5 {-1, 0, -3, 0, -2, 0};
vector<int> nums6 {-1};
vector<int> nums7 {-1, 1};
vector<int> nums8 {-1, -1};

int main() {
  assert(findMaxProduct(nums1) == 48);
  assert(findMaxProduct(nums2) == 15);
  assert(findMaxProduct(nums3) == 1440);
  assert(findMaxProduct(nums4) == 6);
  assert(findMaxProduct(nums5) == 0);
  assert(findMaxProduct(nums6) == -1);
  assert(findMaxProduct(nums7) == 1);
  assert(findMaxProduct(nums8) == 1);

  return 0;
}