Number Container System

Design a system that stores numbers in "containers" (indexed slots) and supports two main operations:

1.change(index, number):
Set the container at the specified index to the given number. If a container already has a number, replace it with the new number.

2. find(number):
   Return the smallest index that currently contains the specified number. If no container holds that number, return -1.

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How It Works

• Initialization:
  When the system is created, all containers are empty.
• Updating a Container:
  When you call change(index, number), the system stores number at that index. If the container already held a number, it is replaced.
• Searching for a Number:
  When you call find(number), the system searches for all containers containing that number and returns the smallest index among them. If none is found, it returns -1.

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Example Test Cases

Example 1

Input:

["NumberContainers", "change", "change", "find", "change", "find"] [[], [2, 10], [5, 10], [10], [2, 20], [10]]

Expected Output:

[null, null, null, 2, null, 5]

Step-by-Step Explanation:

1. Initialization:

   • Create a new NumberContainers instance.

2. Operation: change(2, 10)

   • Set the container at index 2 to 10.

3. Operation: change(5, 10)

   • Set the container at index 5 to 10.

4. Operation: find(10)

   • Check all containers for the number 10.
   • Containers 2 and 5 contain 10.
   • The smallest index among these is 2.
   • Output: 2

5. Operation: change(2, 20)

   • Update the container at index 2 to 20.
   • Now, container 2 no longer holds 10.

6. Operation: find(10)

   • Check all containers for the number 10.
   • Only container 5 now holds 10.
   • Output: 5

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Alternative Example 2

Input:

["NumberContainers", "change", "find", "change", "change", "find", "change", "find", "find"] [[], [3, 15], [15], [7, 15], [3, 20], [15], [7, 30], [15], [20]]

Expected Output:

[null, null, 3, null, null, 7, null, -1, 3]

Step-by-Step Explanation:

1. Initialization:

   • Create a new NumberContainers instance.

2. Operation: change(3, 15)

   • Set the container at index 3 to 15.

3. Operation: find(15)

   • Check all containers for the number 15.
   • Container 3 contains 15.
   • Output: 3

4. Operation: change(7, 15)

   • Set the container at index 7 to 15.
   • Now, containers 3 and 7 both have 15.

5. Operation: change(3, 20)

   • Update the container at index 3 to 20.
   • Container 3 no longer holds 15; only container 7 holds 15.

6. Operation: find(15)

   • Check all containers for the number 15.
   • Only container 7 contains 15.
   • Output: 7

7. Operation: change(7, 30)

   • Update the container at index 7 to 30.
   • Container 7 no longer holds 15.

8. Operation: find(15)

   • Check all containers for the number 15.
   • No container holds 15.
   • Output: -1

9. Operation: find(20)

   • Check all containers for the number 20.
   • Container 3 holds 20.
   • Output: 3

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Constraints

• 1 <= index, number <= 10^9
• There will be at most 10^5 calls combined to the change and find operations.

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