棧還是用的上一篇的數組模擬棧,并在此之上增加了

判斷是否是一個運算符的方法

獲取運算符的優先級方法

計算結果方法

查看棧頂元素的方法

四個方法,具體代碼如下:

package com.ebiz.stack;/*** @author YHj* @create 2019-07-20 14:20* 數組模擬棧*/public class ArrayStack {private int maxSize;private int [] arr; //數組模擬棧 private int top = -1;//構造方法,初始化數組public ArrayStack(int maxSize) {this.maxSize=maxSize;this.arr = new int[maxSize];}//驗證棧滿public boolean isFull(){return top == maxSize-1;}//驗證為空public boolean isEmpty(){return top == -1;}//入棧public void push(int value){if (isFull()){System.out.println("棧已滿");return;}top++;arr[top]=value;}//出棧public int pop(){if(isEmpty()){throw new RuntimeException("棧已空");}int value=arr[top];top--;return value;}//遍歷棧public void list(){if (isEmpty()){throw new RuntimeException("棧為空");}while (true){if (isEmpty()){System.out.println("棧為空");break;}System.out.printf("出站元素為%d%n",arr[top]);top--;}}//返回運算符的優先級 優先級用數字表示//數字越大,代表優先級越高// *或者/ 優先級為1// +或者- 優先級為0// -1 代表運算符為問題運算符public int priority(int operator){if ('*' == operator || '/' == operator){return 1;}else if ('+' == operator || '-' == operator){return 0;}else{return -1;}}//判斷是否為一個運算符public boolean isOperator(char operator){return operator == '+' || operator == '-' || operator == '*' || operator == '/';}//計算方法public int calculator(int num01,int num02,int operator){//用于存放計算結果int result=0;switch (operator){case '+':result = num01+num02;break;case '-':result = num02-num01;break;case '*':result = num01*num02;break;case '/':result = num02/num01;break;default:break;}return result;}//獲取符號棧的棧頂符號,并不是真正取出該元素public int peek() {return arr[top];} }

下面給出測試,中綴表達式提前給定好,只涉及到了兩位數,對于小括號還有小數點后面會將中綴轉為后綴,便于計算

package com.ebiz.stack;/*** @author YHj* @create 2019-07-22 11:04* 棧模擬計算器 中綴表達式*/ public class Calculator {public static void main(String[] args) {//表達式//String expression = "50+2*6-2";String expression = "5-2*3+1";//創建數字棧ArrayStack numeStack = new ArrayStack(10);//創建運算符棧ArrayStack operatorStack = new ArrayStack(10);//初始化索引,用于掃描表達式int index = 0;int num01 = 0;int num02 = 0;int operator = ' '; //定義運算符int res =0; //存放結果char ch =' '; //將每次掃描得到的char保存到ch// 定義字符串,拼接多位數String str="";while (true){//開始掃描表達式,并判斷是數字還是符號ch=expression.substring(index,index+1).charAt(0);//如果為運算符if (operatorStack.isOperator(ch)){//判斷符號棧是否為空 符號棧不為空if (!operatorStack.isEmpty()){//判斷符號優先級 當前符號優先級小于或者等于符號棧頂的符號的優先級,//從數字棧彈出兩個數字,符號棧彈出棧頂符號,進行計算,結果加入數字棧,當前符號加入符號棧if (operatorStack.priority(ch) <= operatorStack.priority(operatorStack.peek())){num01=numeStack.pop();num02=numeStack.pop();operator=operatorStack.pop();//進行計算res=numeStack.calculator(num01,num02,operator);operatorStack.push(ch);numeStack.push(res);}else { //當前符號的優先級大于符號棧頂的符號的優先級,則直接加入符號棧 operatorStack.push(ch);}}else { //符號棧為空 operatorStack.push(ch);}}else {//不是運算符 直接進入樹棧//ASCII表, 查出來的是'1' 對應的十進制為49//numeStack.push(ch-48);//某一字符為多位數時,需要當成字符串處理str+=ch;//判斷ch是否為最后一個字符if (index == expression.length()-1){numeStack.push(Integer.parseInt(str));}else {//判斷下一位是否是字符,下一位是字符,則將當前拼接字符串存入數字棧if (operatorStack.isOperator(expression.substring(index+1,index+2).charAt(0))){numeStack.push(Integer.parseInt(str));//把str 清空str = "";}}}//繼續掃描,索引增加,并判斷是否到最后index++;if (index >= expression.length()){break;}}//表達式掃描完畢后,對兩個棧中元素進行計算while (true){num01=numeStack.pop();num02=numeStack.pop();operator=operatorStack.pop();numeStack.push(numeStack.calculator(num01, num02, operator));//判斷結束if (operatorStack.isEmpty()){break;}}//輸出結果System.out.println("result="+numeStack.pop());}}

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轉載于:https://www.cnblogs.com/jiushixihuandaqingtian/p/11241049.html

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