algorithm - How to implement 3 stacks with one array? - Stack Overflow

down vote accepted

Space (not time) efficient. You could:

1) Define two stacks beginning at the array endpoints and growing in opposite directions.

2) Define the third stack as starting in the middle and growing in any direction you want.

3) Redefine the Push op, so that when the operation is going to overwrite other stack, you shift the whole middle stack in the opposite direction before Pushing.

You need to store the stack top for the first two stacks, and the beginning and end of the third stack in some structure.

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