BuySellStock2.md

Problem statement: Given an integer array prices where prices[i] is the price of a stock on the i-th day, find the maximum profit you can achieve. You may buy and sell the stock multiple times, but you may not hold more than one share at a time.

Examples:

Input: prices = [7,1,5,3,6,4]    Output: 7
Input: prices = [1,2,3,4,5]      Output: 4
Input: prices = [7,6,4,3,1]      Output: 0

Algorithmic Steps (Greedy — accumulate positive daily gains):

1. Initialize maxProfit = 0.
2. Iterate from index 1 to end.
3. If prices[i] - prices[i-1] > 0, add that difference to maxProfit.
4. Return maxProfit.

Algorithmic Steps (Peak-Valley):

1. Initialize maxProfit = 0, i = 0.
2. While i < prices.length - 1:
   • Advance i while prices[i] >= prices[i+1] to find the next valley.
   • Advance i while prices[i] <= prices[i+1] to find the next peak.
   • Add peak - valley to maxProfit.
3. Return maxProfit.

Time and Space complexity:

Approach	Time Complexity	Space Complexity
Greedy (positive daily gains)	O(n)	O(1)
Peak-Valley	O(n)	O(1)