LeetCode 901. Online Stock Span

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本文介绍了一个名为 StockSpanner 的类，该类收集股票每日价格并返回当前价格的跨度。跨度定义为从当前日期开始向后数最大连续天数，期间股票价格不大于当天的价格。文章通过一个示例解释了如何使用该类进行计算。

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Write a class StockSpanner which collects daily price quotes for some stock, and returns the span of that stock's price for the current day.

The span of the stock's price today is defined as the maximum number of consecutive days (starting from today and going backwards) for which the price of the stock was less than or equal to today's price.

For example, if the price of a stock over the next 7 days were [100, 80, 60, 70, 60, 75, 85], then the stock spans would be [1, 1, 1, 2, 1, 4, 6].

Example 1:

Input: ["StockSpanner","next","next","next","next","next","next","next"], [[],[100],[80],[60],[70],[60],[75],[85]]
Output: [null,1,1,1,2,1,4,6]
Explanation: 
First, S = StockSpanner() is initialized.  Then:
S.next(100) is called and returns 1,
S.next(80) is called and returns 1,
S.next(60) is called and returns 1,
S.next(70) is called and returns 2,
S.next(60) is called and returns 1,
S.next(75) is called and returns 4,
S.next(85) is called and returns 6.

Note that (for example) S.next(75) returned 4, because the last 4 prices
(including today's price of 75) were less than or equal to today's price.

Note:

Calls to StockSpanner.next(int price) will have 1 <= price <= 10^5.
There will be at most 10000 calls to StockSpanner.next per test case.
There will be at most 150000 calls to StockSpanner.next across all test cases.
The total time limit for this problem has been reduced by 75% for C++, and 50% for all other languages.

class StockSpanner {
public:
    vector<int> v;
    vector<int> vn;
    StockSpanner() {
        ;
    }
    int next(int price) {
        v.push_back(price);
        int sum=1;
        int n=v.size();
        if(n-2>=0&&v[n-1]==v[n-2])
            sum=vn[n-2]+1;
        else
        {
            for(int i=n-2;i>=0;--i)
            {
                if(v[n-1]>=v[i])
                    ++sum;
                else
                    break;
            }
        }
        vn.push_back(sum);
        return sum;
    }
};

/**
 * Your StockSpanner object will be instantiated and called as such:
 * StockSpanner obj = new StockSpanner();
 * int param_1 = obj.next(price);
 */