Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 8

Description

Design a Number Container System

Design a number container system that can do the following:

• Insert or Replace a number at the given index in the system.
• Return the smallest index for the given number in the system.

Implement the NumberContainers class:

• NumberContainers() Initializes the number container system.
• void change(int index, int number) Fills the container at index with the number. If there is already a number at that index, replace it.
• int find(int number) Returns the smallest index for the given number, or -1 if there is no index that is filled by number in the system.

Example 1:

Input
["NumberContainers", "find", "change", "change", "change", "change", "find", "change", "find"]
[[], [10], [2, 10], [1, 10], [3, 10], [5, 10], [10], [1, 20], [10]]
Output
[null, -1, null, null, null, null, 1, null, 2]

Explanation
NumberContainers nc = new NumberContainers();
nc.find(10); // There is no index that is filled with number 10. Therefore, we return -1.
nc.change(2, 10); // Your container at index 2 will be filled with number 10.
nc.change(1, 10); // Your container at index 1 will be filled with number 10.
nc.change(3, 10); // Your container at index 3 will be filled with number 10.
nc.change(5, 10); // Your container at index 5 will be filled with number 10.
nc.find(10); // Number 10 is at the indices 1, 2, 3, and 5. Since the smallest index that is filled with 10 is 1, we return 1.
nc.change(1, 20); // Your container at index 1 will be filled with number 20. Note that index 1 was filled with 10 and then replaced with 20. 
nc.find(10); // Number 10 is at the indices 2, 3, and 5. The smallest index that is filled with 10 is 2. Therefore, we return 2.

Constraints:

• 1 <= index, number <= 109
• At most 105 calls will be made in total to change and find.

Solution

class NumberContainers {
  map<int, set<int>> indice;
  map<int, int> numbers;
public:
  NumberContainers() { }
  
  void change(int index, int number) {
    if(numbers.count(index)) {
      indice[numbers[index]].erase(index);
    }
    indice[number].insert(index);
    numbers[index] = number;
  }
  
  int find(int number) {
    if(indice[number].empty()) return -1;
    return *indice[number].begin();
  }
};

// Accepted
// 45/45 cases passed (163 ms)
// Your runtime beats 8.66 % of cpp submissions
// Your memory usage beats 6.27 % of cpp submissions (198.1 MB)