LeetCode - Online Stock Span

real_lisa

于 2019-04-15 05:57:44 发布

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本文链接：https://blog.youkuaiyun.com/real_lisa/article/details/89305041

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本文介绍了解决股票跨度问题的两种算法：动态规划（DP）和栈（Stack）。动态规划方法通过比较当前价格与历史价格来计算跨度，而栈方法则利用栈的特性，当遇到更高价格时弹出栈顶元素直到条件不满足。两种方法均能高效地解决股票跨度问题。

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解法一 DP

class StockSpanner {
public:
    StockSpanner() {}
    
    int next(int price) {
        if(prices.empty() || price<prices.back()){
            dp.push_back(1);
        }else {
            int j=dp.size()-1;
            while(j>=0 && prices[j]<=price){
                j -= dp[j];
            }
            dp.push_back(dp.size()-j);
        }
        prices.push_back(price);
        return dp.back();
    }
private:
    vector<int> dp, prices;
};

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

解法二 stack

class StockSpanner {
public:
    StockSpanner() {}
    
    int next(int price) {
        int span = 1;
        while(!s.empty() && price >= s.top().first){
            span += s.top().second;
            s.pop();
        }
        s.emplace(price, span);
        return span;
    }
private:
    stack<pair<int,int>> s;
};

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