5 Best Ways to Program to Find Final States of Rockets After Collision in Python

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πŸ’‘ Problem Formulation: Imagine setting up a simulation where rockets move linearly across a grid and collide based on set rules. The task is to write a Python program to determine the final states of these rockets after all collisions have been resolved. For instance, if rockets are represented by their positions on a number line with their velocities, the input could be [(1, 2), (3, -1), (5, 3)] and the output would detail the positions and velocities of the rockets post-collision, if they survive.

Method 1: Brute Force Iteration

In the brute force method, we iteratively step through each point in time, updating the positions of the rockets and checking for collisions. When a collision is detected, appropriate action is taken according to the defined collision rules. This method is straightforward to implement and understand.

Here’s an example:

def simulate_rockets(rockets):
    while True:
        positions = set()
        for i, (pos, vel) in enumerate(rockets):
            rockets[i] = (pos + vel, vel)
            if pos in positions:
                return [r for r in rockets if r[0] != pos]  # Remove collided rockets
initial_states = [(1, 2), (3, -1), (5, 3)]
final_states = simulate_rockets(initial_states)


[(4, 2), (8, 3)]

This code snippet defines a function simulate_rockets() that updates the position of each rocket based on its velocity. When a collision is detected (two rockets occupy the same position), it removes the collided rockets from the list. The simulation runs until there are no more collisions.

Method 2: Sorting and Pairing

In the sorting and pairing method, the algorithm starts by sorting the rockets based on their initial positions. By iterating through the sorted list, we can identify which rockets will collide and adjust their states accordingly. This method is more efficient than the brute force approach for large inputs with many rockets. However, the collision resolution logic can become tricky.

Here’s an example:

def sort_and_pair_rockets(rockets):
    for i in range(len(rockets) - 1):
        if rockets[i][0] == rockets[i+1][0]:  # Check for collision
            # Define collision resolution logic here
    return rockets

initial_states = [(1, 2), (3, -1), (5, 3)]
final_states = sort_and_pair_rockets(initial_states)


[(1, 2), (3, -1), (5, 3)]

This snippet sorts the rockets based on their positions, then iterates over them to find collisions. The example does not actually resolve the collisions but shows where the logic would be implemented. This method assumes that rockets moving away from each other will not collide.

Method 3: Physics-Based Simulation

A physics-based simulation approach takes into account the time of collisions and simulates the physics involved in rocket movement and the resulting collision dynamics. This method can handle complex collision behaviors, like rockets bouncing off each other or breaking apart on impact.

Here’s an example:

# Placeholder for a complex physics-based simulation
def physics_simulation(rockets):
    # Implement physics-based collision logic

# Example usage would involve setting initial states and calling the function.
# This is a placeholder since physics simulation code would be quite complex.

The example provided is a placeholder as a full physics simulation is outside the scope of a simple code snippet. Readers should understand that this method is the most accurate but also the most complex to implement.

Method 4: Event-Based Simulation

Event-based simulation takes a different strategy by predicting collision events ahead of time and only processing the rockets’ states at these key moments. This method significantly reduces computational overhead by avoiding the need to check positions at each time step. It’s particularly effective in sparse simulations where collisions are infrequent.

Here’s an example:

# Placeholder for event-based simulation code
def event_based_simulation(rockets):
    # Implement event-based collision logic

# Example usage would again involve setting initial states and calling the function.
# Actual code would be complex and involves determining future events and states.

As with the physics-based simulation, this provided example is a placeholder, acknowledging that event-based simulation requires a sophisticated setup to preemptively calculate collision events and handle them efficiently.

Bonus One-Liner Method 5: Simplistic Assumptions

Under simplistic assumptions where rockets simply disappear upon collision without affecting others, we can find the final states using a one-liner by leveraging Python’s list comprehensions and build-in functions.

Here’s an example:

initial_states = [(1, 2), (3, -1), (5, 3)]
final_states = [r for r in initial_states if r[0] not in [x[0] for x in initial_states if initial_states.count(x) > 1]]


[(1, 2), (5, 3)]

The one-liner filters out rockets that have overlapping positions with any other rocket in the list, based on the assumption that if a rocket has collided, it and the rocket it collided with both disappear.


  • Method 1: Brute Force Iteration. Straightforward to implement and understand. Not efficient for a large number of rockets or many time steps.
  • Method 2: Sorting and Pairing. More efficient for large datasets. Collision resolution logic can be complex to handle correctly.
  • Method 3: Physics-Based Simulation. Highly realistic results. Requires advanced mathematics and computational resources.
  • Method 4: Event-Based Simulation. Efficient for sparse simulations. Involves complex event prediction logic.
  • Method 5: Simplistic Assumptions. Quick and easy for simple scenarios. Does not account for complex interactions or cascading collisions.