121.go

package easy_collection

import "math"

/**
 * 121. Best Time to Buy and Sell Stock
 * <p>
 * Say you have an array for which the ith element is the price of a given stock on day i.
 * <p>
 * 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.
 * <p>
 * Note that you cannot sell a stock before you buy one.
 * <p>
 * Example 1:
 * <p>
 * Input: [7,1,5,3,6,4]
 * Output: 5
 * <p>
 * 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.
 * <p>
 * Example 2:
 * <p>
 * Input: [7,6,4,3,1]
 * Output: 0
 * <p>
 * Explanation: In this case, no transaction is done, i.e. max profit = 0.
 */

func maxProfit(prices []int) int {
	minPrice := math.MaxInt32
	target := 0
	for _, p := range prices {
		if p < minPrice {
			minPrice = p
		} else if p-minPrice > target {
			target = p - minPrice
		}
	}
	return target
}