【LeetCode】Best Time to Buy and Sell Stock

先找到第一个波谷，如果比已知波谷还小则更新最小波谷。再找接邻的波峰，如果波峰值减最小波谷值大于已知最大差值则更新。依次处理剩下的波峰及波谷即可。

class Solution {
public:
    int maxProfit(vector<int> &prices) {
        if(prices.size()<2) return 0;
        int min=0x7fffffff;
        int re=0;
        int j=0;
        while(j<prices.size()-1)
        {
            while(j<prices.size()-1&&prices[j]>=prices[j+1]) j++;
            if(prices[j]<min) min=prices[j];
            while(j<prices.size()-1&&prices[j]<prices[j+1]) j++;
            if(prices[j]-min>re) re=prices[j]-min;
        }
        return re;
    }
};