Merge pull request #33 from anxinJ/master

Master

group23/1028361767/data-structure/src/com/coding/basic/Stack.java → group23/1028361767/data-structure/src/com/coding/basic/stack/Stack.java

@@ -1,4 +1,4 @@
-package com.coding.basic;
+package com.coding.basic.stack;
 
 import java.util.EmptyStackException;
 
@@ -13,12 +13,12 @@ public void push(Object o) {
 
     public Object pop() {
         checkBound();
-        return elementData.get(size() - 1);
+        return elementData.remove(size() - 1);
     }
 
     public Object peek() {
         checkBound();
-        return elementData.remove(size() - 1);
+        return elementData.get(size() - 1);
     }
 
     public boolean isEmpty() {
@@ -34,4 +34,14 @@ private void checkBound() {
             throw new EmptyStackException();
         }
     }
+
+    public String toString(){
+    	StringBuilder sb = new StringBuilder();
+    	for(int i=0;i<elementData.size();i++){
+    		sb.append(elementData.get(i));
+    		if(i < elementData.size() - 1)
+    			sb.append(",");
+    	}
+    	return sb.toString();
+    }
 }

group23/1028361767/data-structure/src/com/coding/basic/stack/StackUtil.java

@@ -0,0 +1,99 @@
+package com.coding.basic.stack;
+
+public class StackUtil {
+
+
+	/**
+	 * 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) {
+		Stack tmp = new Stack();
+		Stack tmp1 = new Stack();
+		while(!s.isEmpty())
+			tmp.push(s.pop());
+		while(!tmp.isEmpty())
+			tmp1.push(tmp.pop());
+		while(!tmp1.isEmpty())
+			s.push(tmp1.pop());
+	}
+
+	/**
+	 * 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) {
+		Stack tmp = new Stack();
+		boolean found = false;
+		while(!s.isEmpty() && !found){
+			Object obj = s.pop();
+			if(obj == o){
+				found = true;
+			}else{
+				tmp.push(obj);
+			}
+		}
+		while(!tmp.isEmpty())
+			s.push(tmp.pop());
+	}
+
+	/**
+	 * 从栈顶取得len个元素, 原来的栈中元素保持不变
+	 * 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 len
+	 * @return
+	 */
+	public static Object[] getTop(Stack s,int len) {
+		Object[] objs = new Object[len];
+		if(s.isEmpty() || len == 0)
+			return objs;
+		int i = 0;
+		while(i < len && !s.isEmpty()){
+			objs[i++] = s.pop();
+		}
+		for(i=objs.length-1;i>=0;i--)
+			s.push(objs[i]);
+		return objs;
+	}
+	/**
+	 * 字符串s 可能包含这些字符：  ( ) [ ] { }, a,b,c... x,yz
+	 * 使用堆栈检查字符串s中的括号是不是成对出现的。
+	 * 例如s = "([e{d}f])" , 则该字符串中的括号是成对出现， 该方法返回true
+	 * 如果 s = "([b{x]y})", 则该字符串中的括号不是成对出现的， 该方法返回false;
+	 * 
+	 * ( 40  ) 41 [ 91 ] 93 {123 }125
+	 * @param s
+	 * @return
+	 */
+	public static boolean isValidPairs(String s){
+		if(s == null || s.length() == 0)
+			return true;
+		Stack stack = new Stack();
+		char[] chars = s.toCharArray();
+		for(int i=0;i<chars.length;i++){
+			char tmp = chars[i];
+			if(tmp == 40 || tmp == 91 || tmp == 123){
+				stack.push(tmp);
+				continue;
+			}else if(tmp == 41){
+				if(tmp-1 == (char)stack.peek()){
+					stack.pop();
+				}else{
+					return false;
+				}
+			}else if(tmp == 93 || tmp == 125){
+				if(tmp-2 == (char)stack.peek()){
+					stack.pop();
+				}else{
+					return false;
+				}
+			}
+		}
+		System.out.println(stack.size());
+		if(!stack.isEmpty()) return false;
+		return true;
+	}
+
+
+}

group23/1028361767/data-structure/src/com/coding/basic/stack/expr/InfixExpr.java

@@ -0,0 +1,101 @@
+package com.coding.basic.stack.expr;
+
+import com.coding.basic.stack.Stack;
+
+public class InfixExpr {
+	String expr = null;
+
+	public InfixExpr(String expr) {
+		this.expr = expr;
+	}
+
+	public float evaluate() {
+		if(expr == null || "".equals(expr)){
+			return 0;
+		}
+		Stack numStack = new Stack();
+		Stack opStack = new Stack();
+		String[] ss = expr.split("");
+		boolean needOper = false;// 需要运算，遇到* / 后置为true
+		boolean foundOper = true;// 遇到运算符
+		String ops = "+-*/";
+		for (int i=0;i<ss.length;i++) {
+			String s = ss[i];
+			if(ops.indexOf(s) != -1){
+				if(needOper){
+					doMulOrDivOp(numStack, (String)opStack.pop());
+					needOper = false;
+				}
+				opStack.push(s);
+				foundOper = true;
+				if("+-".indexOf(s) != -1){
+
+				}else{
+					needOper = true;
+				}
+			}else if(!foundOper){// 未找到运算符前，字符串一直追加
+				String tmp = "";
+				Object obj = numStack.pop();
+				if(obj != null){
+					tmp = (String)obj;
+				}
+				numStack.push(tmp + s);
+			}else if("1234567890".indexOf(s) != -1){
+				numStack.push(s);
+				foundOper = false;
+			}else{
+				throw new RuntimeException("InfixExpr not support " + s + " !");
+			}
+			if((i == ss.length - 1) && needOper){
+				doMulOrDivOp(numStack, (String)opStack.pop());
+			}
+		}
+		if(numStack.size() > 1){
+			doAddOrSubOps(numStack, opStack);
+		}
+		return new Float((String)numStack.pop());
+	}
+
+	/**
+	 * 多个加减
+	 * @param numStack
+	 * @param opStack
+	 */
+	private void doAddOrSubOps(Stack numStack, Stack opStack) {
+		Stack calStack = new Stack();
+		while(numStack.size() > 1){
+			calStack.push(numStack.pop());
+			calStack.push(opStack.pop());
+		}
+		float num1 = new Float((String)numStack.pop());
+		float num2;
+		while(calStack.size() > 0){
+			String op = (String)calStack.pop();
+			num2 = new Float((String)calStack.pop());
+			if("+".equals(op)){
+				num1 += num2;
+			}else{
+				num1 -= num2;
+			}
+		}
+		numStack.push(num1 + "");
+	}
+
+	/**
+	 * 单个乘除
+	 * @param numStack
+	 * @param op
+	 */
+	private void doMulOrDivOp(Stack numStack, String op){
+		float num2 = new Float((String)numStack.pop());
+		float num1 = new Float((String)numStack.pop());
+		String result = null;
+		if("*".equals(op)){
+			result = (num1 * num2) + "";
+		}else{
+			result = (num1 / num2) + "";
+		}
+		numStack.push(result);
+	}
+
+}

group23/1028361767/data-structure/src/com/coding/basic/stack/expr/InfixExprTest.java

@@ -0,0 +1,48 @@
+package com.coding.basic.stack.expr;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+
+public class InfixExprTest {
+
+	@Before
+	public void setUp() throws Exception {
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	@Test
+	public void testEvaluate() {
+		//InfixExpr expr = new InfixExpr("300*20+12*5-20/4");
+		{
+			InfixExpr expr = new InfixExpr("2+3*4+5");
+			Assert.assertEquals(19.0, expr.evaluate(), 0.001f);
+		}
+		{
+			InfixExpr expr = new InfixExpr("3*20+12*5-40/2");
+			Assert.assertEquals(100.0, expr.evaluate(), 0.001f);
+		}
+
+		{
+			InfixExpr expr = new InfixExpr("3*20/2");
+			Assert.assertEquals(30, expr.evaluate(), 0.001f);
+		}
+
+		{
+			InfixExpr expr = new InfixExpr("20/2*3");
+			Assert.assertEquals(30, expr.evaluate(), 0.001f);
+		}
+
+		{
+			InfixExpr expr = new InfixExpr("10-30+50");
+			Assert.assertEquals(30, expr.evaluate(), 0.001f);
+		}
+
+	}
+
+}

group23/1028361767/data-structure/src/com/coding/me/book/algorithms/BasicBinarySearch.java

@@ -0,0 +1,12 @@
+package com.coding.me.book.algorithms;
+
+public class BasicBinarySearch {
+
+	public int findIndex(int[] nums, int target){
+		if(nums.length == 0) return -1;
+
+		int mid = nums.length / 2;
+		return 0;
+	}
+
+}