题解 | #买卖股票的最好时机(二)#

import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        
        int pre = sc.nextInt(), max = 0;
        //不用计算买入卖出时机, 只需要把所有的上涨区间加起来即可
        //空间复杂度: O(1), 计算复杂度: O(n)
        for ( int i=1; i<n; i++){
            int current = sc.nextInt();
            max += (pre < current ? current - pre : 0);
            pre = current;
        }
        System.out.println(max);
    }
}