Challenge - 5 Problems
Stock Trading Master
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Test your skills under time pressure!
❓ Predict Output
intermediate2:00remaining
Maximum Profit with One Transaction
What is the output of the following code that calculates the maximum profit from one buy-sell transaction?
DSA Javascript
function maxProfit(prices) {
let minPrice = Infinity;
let maxProfit = 0;
for (const price of prices) {
if (price < minPrice) minPrice = price;
else if (price - minPrice > maxProfit) maxProfit = price - minPrice;
}
return maxProfit;
}
console.log(maxProfit([7,1,5,3,6,4]));Attempts:
2 left
💡 Hint
Track the lowest price and calculate profit by subtracting it from current price.
✗ Incorrect
The code finds the lowest price first and then calculates the maximum difference (profit) by subtracting the lowest price from the current price. The maximum profit is 5 (buy at 1, sell at 6).
❓ Predict Output
intermediate2:00remaining
Maximum Profit with Unlimited Transactions
What is the output of this code that calculates the maximum profit with unlimited buy-sell transactions?
DSA Javascript
function maxProfit(prices) {
let profit = 0;
for (let i = 1; i < prices.length; i++) {
if (prices[i] > prices[i - 1]) {
profit += prices[i] - prices[i - 1];
}
}
return profit;
}
console.log(maxProfit([7,1,5,3,6,4]));Attempts:
2 left
💡 Hint
Add all positive differences between consecutive days.
✗ Incorrect
The code sums all increases between consecutive days: (5-1)+(6-3) = 4 + 3 = 7.
❓ Predict Output
advanced2:00remaining
Maximum Profit with Cooldown Period
What is the output of this code that calculates maximum profit with a cooldown period after selling?
DSA Javascript
function maxProfit(prices) {
if (prices.length === 0) return 0;
let sell = 0, prev_sell = 0, buy = -Infinity;
for (const price of prices) {
let prev_buy = buy;
buy = Math.max(prev_sell - price, buy);
prev_sell = sell;
sell = Math.max(prev_buy + price, sell);
}
return sell;
}
console.log(maxProfit([1,2,3,0,2]));Attempts:
2 left
💡 Hint
Use variables to track buy and sell states considering cooldown.
✗ Incorrect
The code uses dynamic programming to track buy and sell states with cooldown. The maximum profit is 3.
❓ Predict Output
advanced2:00remaining
Maximum Profit with Transaction Fee
What is the output of this code that calculates maximum profit with a transaction fee for each sell?
DSA Javascript
function maxProfit(prices, fee) {
let cash = 0, hold = -prices[0];
for (let i = 1; i < prices.length; i++) {
cash = Math.max(cash, hold + prices[i] - fee);
hold = Math.max(hold, cash - prices[i]);
}
return cash;
}
console.log(maxProfit([1,3,2,8,4,9], 2));Attempts:
2 left
💡 Hint
Track cash and hold states, subtract fee on sell.
✗ Incorrect
The code tracks cash (profit without stock) and hold (profit with stock). The maximum profit after fees is 8.
🧠 Conceptual
expert3:00remaining
Understanding State Transitions in Stock Trading with Cooldown and Fee
Which option correctly describes the state transitions in a dynamic programming solution for stock trading with both cooldown and transaction fee?
Attempts:
2 left
💡 Hint
Think about how buy and sell states update and how cooldown delays buying after selling.
✗ Incorrect
In DP solutions, buy state updates from previous sell minus price, sell state updates from previous buy plus price minus fee, and cooldown is handled by not allowing immediate buy after sell.