Buy and Sell Stocks All Variants in DSA C - Build from Scratch

Buy and Sell Stocks All Variants

📖 Scenario: You are working on a simple stock trading app. You want to help users find the best way to buy and sell stocks to maximize their profit.The stock prices for a few days are given. You will write code to find the best profit for different trading rules.

🎯 Goal: Build a program that calculates the maximum profit from stock prices with different buying and selling rules.

📋 What You'll Learn

Create an array called prices with exact values: 7, 1, 5, 3, 6, 4

Create an integer variable called n that stores the size of the prices array

Write a function maxProfitSingleTransaction that returns the max profit from one buy and one sell

Write a function maxProfitMultipleTransactions that returns max profit from multiple buys and sells

Print the results of both functions

💡 Why This Matters

🌍 Real World

Stock trading apps and financial analysis tools use these algorithms to help users make smart buy and sell decisions.

💼 Career

Understanding these algorithms is important for software engineers working in finance, trading platforms, and data analysis roles.

1

Create the stock prices array

Create an integer array called prices with these exact values: 7, 1, 5, 3, 6, 4. Also create an integer variable called n that stores the size of the prices array.

DSA C

# Create the prices array and its size
// Your code here

Hint

Use int prices[] = {7, 1, 5, 3, 6, 4}; to create the array and int n = sizeof(prices) / sizeof(prices[0]); to get its size.

2

Add function for max profit with single transaction

Add a function called maxProfitSingleTransaction that takes prices array and n as parameters and returns the maximum profit from one buy and one sell. Use variables minPrice and maxProfit inside the function.

DSA C

#include 

// Write maxProfitSingleTransaction function here
// Your code here

int main() {
    int prices[] = {7, 1, 5, 3, 6, 4};
    int n = sizeof(prices) / sizeof(prices[0]);
    return 0;
}

Hint

Use a for loop starting from 1 to n-1. Track the minimum price seen so far and update max profit if current price minus min price is higher.

3

Add function for max profit with multiple transactions

Add a function called maxProfitMultipleTransactions that takes prices array and n as parameters and returns the maximum profit from multiple buy and sell transactions. Use a for loop to add all positive differences between consecutive days.

DSA C

#include 

int maxProfitSingleTransaction(int prices[], int n) {
    int minPrice = prices[0];
    int maxProfit = 0;
    for (int i = 1; i  maxProfit) {
            maxProfit = prices[i] - minPrice;
        }
    }
    return maxProfit;
}

// Write maxProfitMultipleTransactions function here
// Your code here

int main() {
    int prices[] = {7, 1, 5, 3, 6, 4};
    int n = sizeof(prices) / sizeof(prices[0]);
    return 0;
}

Hint

Loop from 1 to n-1 and add the difference to maxProfit whenever today's price is higher than yesterday's.

4

Print the results of both functions

In main, call maxProfitSingleTransaction(prices, n) and maxProfitMultipleTransactions(prices, n). Print the results with these exact messages:
"Max profit with single transaction: %d\n" and "Max profit with multiple transactions: %d\n".

DSA C

#include 

int maxProfitSingleTransaction(int prices[], int n) {
    int minPrice = prices[0];
    int maxProfit = 0;
    for (int i = 1; i  maxProfit) {
            maxProfit = prices[i] - minPrice;
        }
    }
    return maxProfit;
}

int maxProfitMultipleTransactions(int prices[], int n) {
    int maxProfit = 0;
    for (int i = 1; i  prices[i - 1]) {
            maxProfit += prices[i] - prices[i - 1];
        }
    }
    return maxProfit;
}

int main() {
    int prices[] = {7, 1, 5, 3, 6, 4};
    int n = sizeof(prices) / sizeof(prices[0]);
    // Print max profits below
    // Your code here
    return 0;
}

Hint

Call both functions with prices and n. Use printf to print the results with the exact messages.