Given a set of stock prices modelled over time, determine the best gain from buying and selling the stock.

StockAnalysis.java

import java.io.*;
import java.util.*;

class StockAnalysis {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] nums = new int[n];

    for(int i = 0; i < n; i++) {
      nums[i] = sc.nextInt();
    }

    System.out.println(findBiggestGain(nums));
  }

  public static int findBiggestGain(int[] prices) {
    return findBiggestGain(prices, 0);
  }

  public static int findBiggestGain(int[] prices, int i) {
    int curMin = prices[i];
    int curMax = prices[i];

    i++;

    for(; i < prices.length; i++) {
      if(prices[i] > curMax) {
        curMax = prices[i];
      }
      if(prices[i] < curMin) {
        // Look-ahead guarding
        if(i+1 < prices.length) {
          int diff = findBiggestGain(prices, i);
          // Something ahead of us is better
          if(diff > (curMax - curMin)) {
            return diff;
          }
        }
        // What we have is better
        return curMax - curMin;
      }
    }

    // Ended on a bland note? What we have measured is good then.
    return curMax - curMin;
  }
}