leetcode每日刷题计划-简单篇day11

Num 121 买卖股票的最佳时期 Best Time to Buy and Sell Stock

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int len=prices.capacity();
        if(prices.capacity()==0) return 0;
        int minn=prices[0];
        int maxn=prices[0];
        int ans=0;
        for(int i=0;i<=len-2;i++)
        {
            maxn=prices[i];
            minn=prices[i];
            for(int j=i+1;j<=len-1;j++)
            {
                if(prices[j]>maxn)
                    maxn=prices[j];
            }
            ans=max(ans,maxn-minn);
        }
        return ans;
    }
};

Num 122 买卖股票的最佳时期 || Best Time to Buy and Sell Stock ||

先上一个正确但是TLE的方法。。。

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int ans[50000];
        int len=prices.capacity();
        if(len==0||len==1) return 0;
        memset(ans,0,sizeof(ans));
        if(len==2) return max(0,prices[1]-prices[0]);
        ans[len-2]=max(0,(int)(prices[len-1]-prices[len-2]));
        for(int j=len-3;j>=0;j--)
        {
            for(int i=1;i<len-1-j;i++)
            {
                ans[j]=max(ans[j],max(ans[j+i],ans[j+i]+(int)(prices[j+i]-prices[j])));
            }
        }
        return ans[0];
    }
};

默认里面带的max函数只能处理两个

另外这道题是贪心，刚开始重复计算tle了

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int ans=0;
        int len=prices.capacity();
        for(int i=0;i<len-1;i++)
            ans=ans+max(0,prices[i+1]-prices[i]);
        return ans;
    }
};