cc150_3_1.java

package cc150_3_1;

public class ArrayStack {

	private int[] data;
	private int[] sk_lp = new int[3];
	private int[] sk_hp = new int[3];
	private int[] top_p = new int[3];
	
	public ArrayStack(int capacity) throws Exception{
		if(capacity < 3) {
			throw new Exception("Must larger than 3");
		}
		data = new int[capacity];
		SetPointer(capacity);
	}
	
	private void SetPointer(int capacity){
		int gap = capacity/3;
		for(int i=0;i<3;i++){
			sk_lp[i] = gap*i;
			top_p[i] = sk_lp[i];
			sk_hp[i] = gap*(i+1);
		}
		
	}
	
	public void push(int val, int stackID) throws Exception{
		if(stackID < 0 || stackID>=3){
			throw new Exception("Wrong Stack");
		}
			int top = top_p[stackID];
			int high = sk_hp[stackID];
			if(top == high){
				throw new Exception("Stack Overflow");
			}
			data[top] = val;
		    top_p[stackID]++;
	}
	
	public int pop(int stackID) throws Exception{
		if(stackID < 0 || stackID>=3){
			throw new Exception("Wrong Stack");
		}
		int top = top_p[stackID];
		int low = sk_hp[stackID];
		if(top == low){
			throw new Exception("Stack already empty");
		}
		int temp = data[top];
		top_p[stackID] --;
		return temp;
		
	}
	
}