Best Time to Buy and Sell Stock III

前后两遍遍历，算出当前位置之前和之后的最大利润。

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