the code:
def check(balls):
r = False
for i in balls:
if(i == "R"):
r = True
if(r and i == "L"):
return False
return True
N = 5
Balls_direction = ["L", "R", "R", "L", "R"]
collisionCount = 0
while(not check(Balls_direction)):
for i in range(N-1):
if(Balls_direction[i] == "R" and Balls_direction[i+1] == "L"):
Balls_direction[i] = "L"
Balls_direction[i+1] = "R"
collisionCount += 1
print(collisionCount)
Question: N balls are arranged in a row. Each ball is moving either left (L) or right (R) with the same speed. When two balls collide, they each move to the opposite direction with the same speed as before. How many collisions will happen?
To solve the problem, we can iterate through the list of balls' directions and check if there is any collision between consecutive balls. We repeat this process until there are no more collisions.
Here is a step-by-step walkthrough of the code:
1. The `check` function takes a list of ball directions as input and returns `True` if there are no collisions, and `False` otherwise. It checks if there is any 'R' ball followed by an 'L' ball. If so, it means there are still collisions present.
2. The variable `N` represents the number of balls, which is set to 5.
3. The list `Balls_direction` represents the directions of the balls. Each ball's direction is either 'L' (left) or 'R' (right).
4. The variable `collisionCount` is initialized to 0, which will keep track of the number of collisions.
5. The `while` loop continues until there are no more collisions (i.e., when the `check` function returns `True`).
6. Inside the `while` loop, we iterate through the range from 0 to `N-1`, which represents the indices of the balls in the list.
7. We check if the current ball and the next ball will collide, i.e., if the current ball is moving right ('R') and the next ball is moving left ('L'). If a collision is detected, we swap the directions of these two balls, representing their change in direction upon collision.
8. After each collision, we increment the `collisionCount` variable by 1.
9. Once all collisions have been resolved and the `check` function returns `True`, we exit the `while` loop.
10. Finally, we print the value of `collisionCount`, which represents the total number of collisions.
To calculate how many collisions will happen, we can follow these steps:
1. Initialize `collisionCount` to 0.
2. Check if there are any collisions present by calling the `check` function with the `Balls_direction` list.
3. While there are still collisions (i.e., `check` returns `False`), iterate through the `Balls_direction` list.
4. If a collision is detected, swap the directions of the colliding balls and increment `collisionCount` by 1.
5. Once all collisions have been resolved, print the value of `collisionCount` to get the total number of collisions.