1、

class Solution {    public int maxProfit(int[] prices) {        int len = prices.length;        if(len<=1){            return 0;        }        int min = prices[0];        int max = 0;        for(int i=1;i
     
      max){               max =  prices[i]-min;            }            if(prices[i]
     

 2、

class Solution {    public int maxProfit(int[] prices) {        int maxprofit = 0;        for (int i = 1; i < prices.length; i++) {            if (prices[i] > prices[i - 1])                maxprofit += prices[i] - prices[i - 1];        }        return maxprofit;    }}

 3、

class Solution {        public int maxProfit(int[] prices) {        int len = prices.length;        int min;        int max;        int maxProfile = 0;        int maxProfile1;        int maxProfile2;        List
     
       list1 = new ArrayList<>();        List
      
        list2 = new ArrayList<>();        List
       
         profile1 = new ArrayList<>();        int i=0;        while(i
        
         =prices[i+1]) ++i;            min = prices[i];            while(i
         
          <=prices[i+1]) ++i;            max = prices[i];            list1.add(min);            list2.add(max);        }        int size = list1.size();        if(size==0) {                    }else if(size==1){            return list2.get(0) - list1.get(0);        }else{            min = list1.get(0);            maxProfile1 = list2.get(0)-min;            for(i=0;i
          
           0){ min = Math.min(list1.get(i),min); maxProfile1 = Math.max(list2.get(i)-min,maxProfile1); } profile1.add(maxProfile1); } max = list2.get(size-1); maxProfile2 = max-list1.get(size-1); for(i=size-1;i>0;--i){ if(i