C++ Program for best time to buy and sell

October 11, 2022

Best time to buy and Sell stock in C++

Here, in this page we will discuss the program to find the best time to buy and sell stock in C++  We are given with an array represents the cost of a stock on each day is given in an array, find the max profit that you can make by buying and selling in those days.

Example :

Input: Prices[ ] = [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5. Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.

 
Best time to buy and sell in C++

Algorithm :

  • Take the size of the array from the user and store it in variable say n.
  • Now, declare an array of size n and takes n integer value from the user and store them in array.
  • Create an array named max_sp of size equals size of price array and a variable max and initialize it as the minimum value.
  • Start from the last index in price array.
    1. If prices[i] is greater than max
      1. Update max as prices[i] and make max_sp[i] as minimum value
    2. Else if price[i] is not greater than max
      1. Update max_sp[i] = max.
  • After the pre computation, we follow the naive approach and replace the inner nested loop by using the max_sp array that we just created.
  • Print value of max.
Best time to buy and sell

Code in C++

#include <bits/stdc++.h>
using namespace std;

int maxProfit(int *prices, int n) {

  int max_sp[n];
  int maximum = INT_MIN;

  // Construct the maxSP array
  for (int i = n - 1; i >= 0; i--) {
     if (prices[i] > maximum) {
       maximum = prices[i];
       max_sp[i] = INT_MIN;
     } 
     else {
       max_sp[i] = maximum;
     }
  }

  int profit = 0;
  for (int i = 0; i < n; i++) {

    if (max_sp[i] != INT_MIN) {
      profit = max(profit, max_sp[i] - prices[i]);
   }

  }

  // Return profit
  return profit;
}

int main() {

  int n;
  cin>>n;

  int prices[n];

  for(int i=0; i<n; i++)
    cin>>prices[i];

  // Calculating the max profit
  int ans = maxProfit(prices, n);

  // Print the answer
  cout<<ans<<endl;
  return 0;
}
Input :

6

7 1 5 3 6 4

Output :

5

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