Maximum Product of Two Elements in an Array Solutions in C++

// Source : https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/
// Author : Hao Chen
// Date   : 2020-10-02


class Solution {
public:
    int maxProduct(vector<int>& nums) {
        int max1=max(nums[0], nums[1]);
        int max2=min(nums[0], nums[1]);
        
        for (int i=2; i< nums.size(); i++) {
            if (nums[i] > max1) {
                max2 = max1;
                max1 = nums[i];
                continue;
            }else if (nums[i] > max2) {
                max2 = nums[i];
            }
        }
        return (max1-1)*(max2-1);
    }
};

/// Source : https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/
/// Author : liuyubobobo
/// Time   : 2020-05-30

#include <iostream>
#include <vector>

using namespace std;


/// Brute Force
/// Time Complexity: O(n^2)
/// Space Complexity: O(1)
class Solution {
public:
    int maxProduct(vector<int>& nums) {

        int res = 0;
        for(int i = 0; i < nums.size(); i ++)
            for(int j = i + 1; j < nums.size(); j ++)
                res = max(res, (nums[i] - 1) * (nums[j] - 1));
        return res;
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/
/// Author : liuyubobobo
/// Time   : 2020-06-05

#include <iostream>
#include <vector>

using namespace std;


/// Sorting
/// Time Complexity: O(nlogn)
/// Space Complexity: O(1)
class Solution {
public:
    int maxProduct(vector<int>& nums) {

        sort(nums.begin(), nums.end(), greater<int>());
        return (nums[0] - 1) * (nums[1] - 1);
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/
/// Author : liuyubobobo
/// Time   : 2020-06-05

#include <iostream>
#include <vector>

using namespace std;


/// Linear Scan to find the largest and the second largest
/// Time Complexity: O(n)
/// Space Complexity: O(1)
class Solution {
public:
    int maxProduct(vector<int>& nums) {

        int a = -1, b = -1;
        for(int e: nums)
            if(e >= a) b = a, a = e;
            else if(e > b) b = e;
        return (a - 1) * (b - 1);
    }
};


int main() {

    return 0;
}