Package Matching - Google Top Interview Questions


Problem Statement :


You are given two-dimensional list of integers sales and buyers. 

Each element in sales contains [day, price] meaning that the package is only available for sale on that day for that price. 

Each element in buyers contains [payday, amount] meaning that the buyer has that amount of money to spend on payday and afterwards.

Given that each buyer can buy at most one package, and each package can be sold to at most one person, return the maximum number of packages that can be bought.

Constraints

n ≤ 100,000 where n is the length of buyers

m ≤ 100,000 where m is the length of sales

Example 1

Input

sales = [

    [0, 2],

    [0, 2],

    [0, 3],

    [1, 1],

    [1, 2],

    [3, 1]

]

buyers = [

    [0, 1],

    [0, 3],

    [1, 2]

]

Output

3

Explanation

The first person can take [1, 1] package. The second person can take the [0, 3] package. The last 
person can take the [1, 2] package.


Solution :



title-img 




                        Solution in C++ :

int solve(vector<vector<int>>& sales, vector<vector<int>>& buyers) {
    sort(buyers.begin(), buyers.end());
    sort(sales.begin(), sales.end());
    multiset<int> m;
    int i = sales.size() - 1, j = buyers.size() - 1, ans = 0;
    while (j >= 0) {
        while (i >= 0 and sales[i][0] >= buyers[j][0]) m.insert(sales[i--][1]);
        int p = buyers[j--][1];
        if (!m.empty()) {
            auto x = m.upper_bound(p);
            if (x-- != m.begin()) {
                m.erase(x);
                ans += 1;
            }
        }
    }
    return ans;
}
                    


                        Solution in Java :

import java.util.*;

class Solution {
    void add(TreeMap<Integer, Integer> tm, int val) {
        tm.put(val, tm.getOrDefault(val, 0) + 1);
    }
    void remove(TreeMap<Integer, Integer> tm, int val) {
        tm.put(val, tm.get(val) - 1);
        if (tm.get(val) == 0)
            tm.remove(val);
    }

    public int solve(int[][] sales, int[][] buyers) {
        Arrays.sort(sales, (a, b) -> (a[0] - b[0]));
        Arrays.sort(buyers, (a, b) -> (a[0] - b[0]));
        int n = sales.length - 1, m = buyers.length - 1, res = 0;
        TreeMap<Integer, Integer> tm = new TreeMap();
        while (m >= 0) {
            int payday = buyers[m][0], amount = buyers[m][1];
            while (n >= 0 && sales[n][0] >= payday) {
                add(tm, sales[n][1]);
                n--;
            }
            Integer best_price = tm.floorKey(amount);
            if (best_price != null) {
                remove(tm, best_price);
                res++;
            }
            m--;
        }
        return res;
    }
}
                    


                        Solution in Python : 
                            
class Solution:
    def solve(self, sales, buyers):
        sales.sort()
        buyers.sort()

        ans = j = 0
        offers = SortedList()
        for d, p in sales:
            while j < len(buyers) and buyers[j][0] <= d:
                offers.add(buyers[j][1])
                j += 1

            index = offers.bisect_left(p)
            if index < len(offers):
                offers.pop(index)
                ans += 1

        return ans


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