[leetcode]Best Time to Buy and Sell stock series

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public class Solution { public int maxProfit(int[] prices) { if (prices == null || prices.length <= 1) return 0; int currentMin = prices[0]; int result = 0; for (int i = 1; i < prices.length; i++){ result = Math.max(result, prices[i]-currentMin); currentMin = Math.min(currentMin, prices[i]); } return result; } }

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public class Solution { public int maxProfit(int[] prices) { if (prices == null || prices.length == 0) return 0; int currentStart = 0; int currentEnd = 0; int sum = 0; for (int i = 1; i < prices.length; i++){ if (prices[i] < prices[i-1]){ sum += (prices[currentEnd]-prices[currentStart]); currentStart = currentEnd = i; }else{ currentEnd = i; } } sum += (prices[currentEnd]-prices[currentStart]); return sum; } }

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public class Solution { public int maxProfit(int[] prices) { if (prices == null || prices.length <= 1) return 0; int[] profit = new int[prices.length]; int[] profit_r = new int[prices.length]; findMaxI(prices, profit); findMaxII(prices, profit_r); int max = 0; for (int i = 0; i < prices.length; i++){ max = Math.max(profit[i]+profit_r[i], max); } return max; } private void findMaxII(int[]prices, int profit[]){ int currentMax = prices[prices.length-1]; int last = profit[prices.length-1]; for (int i = prices.length-2; i >= 0; i--){ profit[i] += Math.max(profit[i+1], currentMax-prices[i]); currentMax = Math.max(prices[i], currentMax); } return; } private void findMaxI(int[]prices, int profit[]){ int currentMin = prices[0]; for (int i = 1; i < prices.length; i++){ profit[i] = Math.max(profit[i-1], prices[i]-currentMin); currentMin = Math.min(prices[i], currentMin); } return; } }