描述如何只用一个数组来实现三个栈

题目：描述如何只用一个数组来实现三个栈





int stackSize=100;

int [] buffer=new int [stackSize*3];

int []stackPointer={-1,-1,-1};//用于追踪栈顶元素的指针

void push(int stackNum,int value) throws Exception

{

/*检查有无空闲空间*/

if(stackPointer[stackNum]+1>=stackSize)//最后一个元素

{

throw new Exception("out of space.");

}

//栈指针自增，然后更新栈顶元素的值

stackPointer[stackNum]++;

buffer[absTopOfStack(stackNum)]=value;

}

int pop(int stackNum) throws Exception

{

if(stackPointer[stackNum]==-1)

{

throw new Exception("Trying to pop an empty stack.");

}

int value=buffer[absTopOfStack(stackNum)];//获取栈顶元素

buffer[absTopOfStack(stackNum)]=0;//清零指定索引元素的值

stackPointer[stackNum]--;//指针自减

return value;

}

int peek(int stackNum)

{

int index=absTopOfStack(stackNum);

return buffer[index];

}

boolean isEmpty(int stackNum)

{

return stackPointer[stackNum]==-1;

}

//返回栈“stackNum”栈顶元素的索引，绝对量

int absTopOfStack(int stackNum)

{

return stackNum*stackSize+stackPointer[stackNum];

}