diff --git a/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/QuickMinStack.java b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/QuickMinStack.java new file mode 100644 index 0000000000..9f044cc1f9 --- /dev/null +++ b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/QuickMinStack.java @@ -0,0 +1,37 @@ +package com.github.ipk2015.coding2017.basic.stack; + +import java.util.HashMap; + +/** + * 设计一个栈，支持栈的push和pop操作，以及第三种操作findMin, 它返回改数据结构中的最小元素 + * finMin操作最坏的情形下时间复杂度应该是O(1) ， 简单来讲，操作一次就可以得到最小值 + * @author liuxin + * + */ +public class QuickMinStack { + private Stack normalStack = new Stack(); + private Stack minStack = new Stack(); + public void push(int data){ + normalStack.push(data); + if(minStack.isEmpty()){ + minStack.push(data); + }else{ + if(data <= (Integer)minStack.peek()){ + minStack.push(data); + } + } + } + public int pop(){ + int element = (Integer)normalStack.pop(); + if(element == (Integer)minStack.peek()){ + minStack.pop(); + } + return element; + } + public int peek(){ + return (Integer)normalStack.peek(); + } + public int findMin(){ + return (Integer)minStack.peek(); + } +} diff --git a/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/StackWithTwoQueues.java b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/StackWithTwoQueues.java new file mode 100644 index 0000000000..7d6da60917 --- /dev/null +++ b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/StackWithTwoQueues.java @@ -0,0 +1,42 @@ +package com.github.ipk2015.coding2017.basic.stack; + +import com.github.ipk2015.coding2017.basic.queue.Queue; + +public class StackWithTwoQueues { + + private Queue queue1 = new Queue(); + private Queue queue2 = new Queue(); + + public void push(Object data) { + queue1.enQueue(data); + } + + public Object pop() { + if(queue1.size() == 1){ + return queue1.deQueue(); + } + if(queue2.isEmpty()){ + moveElements(queue1,queue2); + } + return queue2.deQueue(); + } + + private void moveElements(Queue oirQueue,Queue aimQueue){ + if(oirQueue.isEmpty()){ + return; + }else{ + Object element = oirQueue.deQueue(); + moveElements(oirQueue,aimQueue); + aimQueue.enQueue(element); + } + } + + public boolean isEmpty(){ + return queue1.isEmpty() && queue2.isEmpty(); + } + + public int size(){ + return queue1.size()+queue2.size(); + } + +} diff --git a/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/TwoStackInOneArray.java b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/TwoStackInOneArray.java new file mode 100644 index 0000000000..e8e8488fe6 --- /dev/null +++ b/group24/121111914/src/com/github/ipk2015/coding2017/basic/stack/TwoStackInOneArray.java @@ -0,0 +1,83 @@ +package com.github.ipk2015.coding2017.basic.stack; + +/** + * 用一个数组实现两个栈 + * 将数组的起始位置看作是第一个栈的栈底，将数组的尾部看作第二个栈的栈底，压栈时，栈顶指针分别向中间移动，直到两栈顶指针相遇，则扩容。 + * @author liuxin + * + */ +public class TwoStackInOneArray { + Object[] data = new Object[10]; + private int pointer1 = 0; + private int pointer2 = 9; + + /** + * 向第一个栈中压入元素 + * @param o + */ + public void push1(Object o){ + if(pointer1 == pointer2){ + enlargeDataArray(); + } + data[pointer1++] = o; + } + + private void enlargeDataArray(){ + Object[] newData = new Object[data.length+100]; + for(int i = 0;i < pointer1;i++){ + newData[i] = data[i]; + } + for(int i = pointer2+1;i < data.length;i++){ + newData[i+100] = data[i]; + } + pointer2 += 100; + data = newData; + } + /** + * 从第一个栈中弹出元素 + * @return + */ + public Object pop1(){ + Object object = data[pointer1-1]; + data[pointer1-1] = null; + pointer1--; + return object; + } + + /** + * 获取第一个栈的栈顶元素 + * @return + */ + + public Object peek1(){ + return data[pointer1-1]; + } + /* + * 向第二个栈压入元素 + */ + public void push2(Object o){ + if(pointer1 == pointer2){ + enlargeDataArray(); + } + data[pointer2--] = o; + } + /** + * 从第二个栈弹出元素 + * @return + */ + public Object pop2(){ + Object object = data[pointer2+1]; + data[pointer2+1] = null; + pointer2++; + return object; + } + /** + * 获取第二个栈的栈顶元素 + * @return + */ + + public Object peek2(){ + return data[pointer2+1]; + } + +} diff --git a/group24/121111914/src/com/github/ipk2015/coding2017/basic/test/QuickMinStackTest.java b/group24/121111914/src/com/github/ipk2015/coding2017/basic/test/QuickMinStackTest.java new file mode 100644 index 0000000000..f976861dbb --- /dev/null +++ b/group24/121111914/src/com/github/ipk2015/coding2017/basic/test/QuickMinStackTest.java @@ -0,0 +1,56 @@ +package com.github.ipk2015.coding2017.basic.test; + +import static org.junit.Assert.*; + +import org.junit.After; +import org.junit.Before; +import org.junit.Test; + +import com.github.ipk2015.coding2017.basic.stack.QuickMinStack; + +public class QuickMinStackTest { + QuickMinStack stack; + @Before + public void setUp() throws Exception { + stack = new QuickMinStack(); + } + + @After + public void tearDown() throws Exception { + } + + @Test + public void testPush() { + stack.push(11); + assertEquals(11, stack.peek()); + stack.push(22); + assertEquals(22, stack.peek()); + } + + @Test + public void testPop() { + stack.push(11); + stack.push(22); + stack.push(33); + assertEquals(33, stack.pop()); + assertEquals(22, stack.pop()); + assertEquals(11, stack.pop()); + } + + @Test + public void testFindMin() { + + stack.push(4); + stack.push(2); + stack.push(3); + stack.push(5); + assertEquals(2, stack.findMin()); + stack.pop(); + assertEquals(2, stack.findMin()); + stack.pop(); + assertEquals(2, stack.findMin()); + stack.pop(); + assertEquals(4, stack.findMin()); + } + +}