【Leetcode周赛】contest-262 (2021年10月11日)

链接：https://leetcode.com/contest/weekly-contest-262

T1: 2032. Two Out of Three

https://leetcode.com/problems/two-out-of-three/

思路：无

T2: 2033. Minimum Operations to Make a Uni-Value Grid

https://leetcode.com/problems/minimum-operations-to-make-a-uni-value-grid/

 思路：排序找中位数。（为啥能行，其实我也不知道。。）

class Solution {
public:
    int minOperations(vector<vector<int>>& grid, int x) {
        int m = grid.size(), n = grid[0].size();
        vector<int> nums(m * n);
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                nums[j + i * n] = grid[i][j];
            }
        }
        sort(nums.begin(), nums.end());
        int median = nums[(m*n-1)/2];
        int res = 0;
        for (int i = 0; i < nums.size(); ++i) {
            if (abs(nums[i] - median) % x) {
                return -1;
            }
            int times = abs(nums[i] - median) / x;
            res += times;
        } 
        return res;
    }
};

  

T3: 2034. Stock Price Fluctuation

https://leetcode.com/problems/stock-price-fluctuation/Design an algorithm that:

• Updates the price of the stock at a particular timestamp, correcting the price from any previous records at the timestamp.
• Finds the latest price of the stock based on the current records. The latest price is the price at the latest timestamp recorded.
• Finds the maximum price the stock has been based on the current records.
• Finds the minimum price the stock has been based on the current records.

Implement the StockPrice class:

• StockPrice() Initializes the object with no price records.
• void update(int timestamp, int price) Updates the price of the stock at the given timestamp.
• int current() Returns the latest price of the stock.
• int maximum() Returns the maximum price of the stock.
• int minimum() Returns the minimum price of the stock.

思路：我用了两个 map， 做了一个类似倒排索引的结构。

class StockPrice {
public:
    map<int, int> tsToPriceMap;
    map<int, unordered_set<int>> priceToTsMap;
    StockPrice() {
        
    }
    
    void update(int timestamp, int price) {
        if (tsToPriceMap.count(timestamp)) {
            int orignalPrice = tsToPriceMap[timestamp];
            priceToTsMap[orignalPrice].erase(timestamp);
            if (priceToTsMap[orignalPrice].empty()) {
                priceToTsMap.erase(orignalPrice);
            }
        } 
        tsToPriceMap[timestamp] = price;
        priceToTsMap[price].insert(timestamp);
    }
    
    int current() {
        return prev(tsToPriceMap.end())->second;
    }
    
    int maximum() {
        return prev(priceToTsMap.end())->first;
    }
    
    int minimum() {
        return (priceToTsMap.begin())->first;
    }
};

/**
 * Your StockPrice object will be instantiated and called as such:
 * StockPrice* obj = new StockPrice();
 * obj->update(timestamp,price);
 * int param_2 = obj->current();
 * int param_3 = obj->maximum();
 * int param_4 = obj->minimum();
 */

T4: 2035. Partition Array Into Two Arrays to Minimize Sum Difference

https://leetcode.com/problems/partition-array-into-two-arrays-to-minimize-sum-difference/

思路：没有 --- 大坑未补。