marge from liuxin 2017-4-11 CoderXLoong

liuxin/data-structure/src/com/coding/basic/stack/StackUtil.java

@@ -1,23 +1,65 @@
 package com.coding.basic.stack;
-
+import java.util.Stack;
 public class StackUtil {
 
+	public static void bad_reverse(Stack<Integer> s) {
+		if(s == null || s.isEmpty()){
+			return;
+		}
+		Stack<Integer> tmpStack = new Stack();
+		while(!s.isEmpty()){
+			tmpStack.push(s.pop());
+		}
+
+		s = tmpStack;
+
+	}
 
 	/**
 	 * 假设栈中的元素是Integer, 从栈顶到栈底是 : 5,4,3,2,1 调用该方法后， 元素次序变为: 1,2,3,4,5
 	 * 注意：只能使用Stack的基本操作，即push,pop,peek,isEmpty， 可以使用另外一个栈来辅助
 	 */
-	public static void reverse(Stack s) {
-
+	public static void reverse(Stack<Integer> s) {
+		if(s == null || s.isEmpty()){
+			return;
+		}
+		Integer top = s.pop();
+		reverse(s);
+		addToBottom(s,top);
+
+
+	}
+	public static void addToBottom(Stack<Integer> s,  Integer value){
+		if(s.isEmpty()){
+			s.push(value);
+		} else{
+			Integer top = s.pop();
+			addToBottom(s,value);
+			s.push(top);
+		}
+
 	}
-
 	/**
 	 * 删除栈中的某个元素 注意：只能使用Stack的基本操作，即push,pop,peek,isEmpty， 可以使用另外一个栈来辅助
 	 * 
 	 * @param o
 	 */
 	public static void remove(Stack s,Object o) {
-
+		if(s == null || s.isEmpty()){
+			return;
+		}
+		Stack tmpStack = new Stack();
+
+		while(!s.isEmpty()){
+			Object value = s.pop();
+			if(!value.equals(o)){
+				tmpStack.push(value);
+			} 			
+		}
+
+		while(!tmpStack.isEmpty()){
+			s.push(tmpStack.pop());
+		}
 	}
 
 	/**
@@ -27,7 +69,24 @@ public static void remove(Stack s,Object o) {
 	 * @return
 	 */
 	public static Object[] getTop(Stack s,int len) {
-		return null;
+
+		if(s == null || s.isEmpty() || s.size()<len || len <=0 ){
+			return null;
+		}
+
+		Stack tmpStack = new Stack();
+		int i = 0;
+		Object[] result = new Object[len];
+		while(!s.isEmpty()){
+			Object value = s.pop();			
+			tmpStack.push(value);
+			result[i++] = value;
+			if(i == len){
+				break;
+			}
+		}
+
+		return result;
 	}
 	/**
 	 * 字符串s 可能包含这些字符：  ( ) [ ] { }, a,b,c... x,yz
@@ -38,7 +97,39 @@ public static Object[] getTop(Stack s,int len) {
 	 * @return
 	 */
 	public static boolean isValidPairs(String s){
-		return false;
+
+		Stack<Character> stack = new Stack();
+		for(int i=0;i<s.length();i++){
+			char c = s.charAt(i);
+
+			if(c == '(' || c =='[' || c == '{'){
+
+				stack.push(c);
+
+			} else if( c == ')'){
+
+				char topChar = stack.pop();
+				if(topChar != '('){
+					return false;
+				}
+
+			} else if( c == ']'){
+
+				char topChar = stack.pop();
+				if(topChar != '['){
+					return false;
+				}
+
+			} else if( c == '}'){
+
+				char topChar = stack.pop();
+				if(topChar != '{'){
+					return false;
+				}
+
+			}
+		}
+		return stack.size() == 0;
 	}
 
 

liuxin/data-structure/src/com/coding/basic/stack/StackUtilTest.java

@@ -0,0 +1,78 @@
+package com.coding.basic.stack;
+
+import static org.junit.Assert.fail;
+
+import java.util.Stack;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+public class StackUtilTest {
+
+	@Before
+	public void setUp() throws Exception {
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	@Test
+	public void testAddToBottom() {
+		Stack<Integer> s = new Stack();
+		s.push(1);
+		s.push(2);
+		s.push(3);
+
+		StackUtil.addToBottom(s, 0);
+
+		Assert.assertEquals("[0, 1, 2, 3]", s.toString());
+
+	}
+	@Test
+	public void testReverse() {
+		Stack<Integer> s = new Stack();
+		s.push(1);
+		s.push(2);
+		s.push(3);
+		s.push(4);
+		s.push(5);
+		Assert.assertEquals("[1, 2, 3, 4, 5]", s.toString());
+		StackUtil.reverse(s);
+		Assert.assertEquals("[5, 4, 3, 2, 1]", s.toString());
+	}
+
+	@Test
+	public void testRemove() {
+		Stack<Integer> s = new Stack();
+		s.push(1);
+		s.push(2);
+		s.push(3);
+		StackUtil.remove(s, 2);
+		Assert.assertEquals("[1, 3]", s.toString());
+	}
+
+	@Test
+	public void testGetTop() {
+		Stack<Integer> s = new Stack();
+		s.push(1);
+		s.push(2);
+		s.push(3);
+		s.push(4);
+		s.push(5);
+		{
+			Object[] values = StackUtil.getTop(s, 3);
+			Assert.assertEquals(5, values[0]);
+			Assert.assertEquals(4, values[1]);
+			Assert.assertEquals(3, values[2]);
+		}
+	}
+
+	@Test
+	public void testIsValidPairs() {
+		Assert.assertTrue(StackUtil.isValidPairs("([e{d}f])"));
+		Assert.assertFalse(StackUtil.isValidPairs("([b{x]y})"));
+	}
+
+}