Best Time to Buy and Sell Stock

Source

1. lintcode
2. leetcode

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 (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.

Analysis

The problem can be solved using greedy algorithm. We use a vairable to keep track of the min price seen so far, and update the max profit using the new price.

Corner Cases

1. Array Length <= 1.

Complexity

Time: O(n)

Space: O(1)

Code

public class Solution {
  public int maxProfit(int[] prices) {
    if (prices == null || prices.length <= 1) {
      return 0;
    }

    int minPrice = prices[0];
    int maxProfit = 0;
    for (int i = 1; i < prices.length; ++i) {
      maxProfit = Math.max(maxProfit, prices[i] - minPrice);
      minPrice = Math.min(minPrice, prices[i]);
    }
    return maxProfit;
  }
}