121.best-time-to-buy-and-sell-stock.java

/*
 * @lc app=leetcode id=121 lang=java
 *
 * [121] Best Time to Buy and Sell Stock
 *
 * https://leetcode.com/problems/best-time-to-buy-and-sell-stock/description/
 *
 * algorithms
 * Easy (50.55%)
 * Likes:    6312
 * Dislikes: 273
 * Total Accepted:    1M
 * Total Submissions: 2M
 * Testcase Example:  '[7,1,5,3,6,4]'
 *
 * Say you have an array for which the i^th 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.
 * 
 * 
 */

// @lc code=start
class Solution {
    public int maxProfit(int[] prices) {
        
            int maxProfit = 0;
            
            if(prices.length<=0){
                return 0;
            }
            
            int min = prices[0];
            
            for(int i=0;i<prices.length;i++){
                if(prices[i]>min){
                    maxProfit = Math.max(maxProfit,prices[i]-min); 
                }
                else{
                    min=prices[i];
                }
            }
            
            return maxProfit;
    }
}
// @lc code=end