Best Time to Buy and Sell Stock (No more than one transaction)

public class Solution {
    public int maxProfit(int[] prices) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(0 == prices.length) return 0;
        int buy = 0, sell = 0, profit = prices[sell]-prices[buy];
        for(int i=1; i<prices.length-1; i++)
        {
            if(prices[i-1]>=prices[i] && prices[i]<prices[i+1])   //bottom
            {
                if(prices[i]<prices[buy])
                    buy = i;
            }
            if(prices[i-1]<prices[i] && prices[i]>=prices[i+1])   //top
            {
                    sell = i;
            }
            if(sell>buy)
            {
                profit = (prices[sell] - prices[buy])>profit ? prices[sell] - prices[buy] : profit;
            }
        }
        sell = prices.length-1;  //check the last day
        profit = (prices[sell] - prices[buy])>profit ? prices[sell] - prices[buy] : profit;
        return profit;
    }
}