1.使用數組實現大小固定的棧(使用變量index來模擬棧中的指針)
public static class ArrayStack {
private Integer[] arr;
private Integer size;
public ArrayStack(int initSize) {
if (initSize < 0) {
throw new IllegalArgumentException("The init size is less than 0");
}
arr = new Integer[initSize];
size = 0;
}
public Integer peek() {
if (size == 0) {
return null;
}
return arr[size - 1];
}
public void push(int obj) {
if (size == arr.length) {
throw new ArrayIndexOutOfBoundsException("The queue is full");
}
arr[size++] = obj;
}
public Integer pop() {
if (size == 0) {
throw new ArrayIndexOutOfBoundsException("The queue is empty");
}
return arr[--size];
}
}
public static void main(String[] args) {
}
2.使用數組來實現固定大小的隊列
public static class ArrayQueue {
private Integer[] arr;
private Integer size;//當前數組中存放的數字,要求size<arr.length
private Integer first;//下次數字進數組的位置,只要size<arr.length,那麼當first已經到數組的底部則回到頭部
private Integer last;//隊列中出隊的位置,只要隊列中有數,則出隊last++,若++超出,則也回到頭部
public ArrayQueue(int initSize) {
if (initSize < 0) {
throw new IllegalArgumentException("The init size is less than 0");
}
arr = new Integer[initSize];
size = 0;
first = 0;
last = 0;
}
public Integer peek() {
if (size == 0) {
return null;
}
return arr[first];
}
public void push(int obj) {
if (size == arr.length) {
throw new ArrayIndexOutOfBoundsException("The queue is full");
}
size++;
arr[last] = obj;
last = last == arr.length - 1 ? 0 : last + 1;
}
public Integer poll() {
if (size == 0) {
throw new ArrayIndexOutOfBoundsException("The queue is empty");
}
size--;
int tmp = first;
first = first == arr.length - 1 ? 0 : first + 1;
return arr[tmp];
}
}