121. Best Time to Buy and Sell Stock
Tags: ‘Array’, ‘Dynamic Programming’
Say you have an array for which the ith element is the price of a given stock on day i.
If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.
Note that you cannot sell a stock before you buy one.
Example 1:
Input: [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. Not 7-1 = 6, as selling price needs to be larger than buying price.
Example 2:
Input: [7,6,4,3,1] Output: 0 Explanation: In this case, no transaction is done, i.e. max profit = 0.
Solution
public int maxProfit(int[] prices) {
// One pass while maintaining two variable
// minPrice: currently recorded min price
// maxProfit: currently recorded max profit
int minPrice = Integer.MAX_VALUE;
int maxProfit = 0;
for (int p: prices) {
if (p < minPrice) {
minPrice = p;
} else if (p - minPrice > maxProfit) {
maxProfit = p - minPrice;
}
}
return maxProfit;
}