思路分析代码实现 package org.structure.stack;
/**
* 使用栈实现综合计算器
* @author cjj_1
* @date 2020-08-06 10:30
*/
public class IntegratedCalculatorStack {
public static void main(String[] args) {
//定义要计算的表达式
String expresion = "300+8*4-4";
//定义两个栈 分别存放 操作数，和操作符
Stack4Calcalator numStack = new Stack4Calcalator(10);
Stack4Calcalator operStack = new Stack4Calcalator(10);
//定义辅助变量
int index=0;
int num1;
int num2;
int oper;
int res =0;
char ch ;
String keepNum;
//开始遍历 表达式
while (expresion.length() != index){
ch = expresion.charAt(index);
if(isOper(ch)){//如果是操作符
if(operStack.isEmpty()){
operStack.pushOne(ch);
}else {//如果不是空的比对栈顶元素的的优先级
if(priority(ch)<=priority(operStack.picck())){
oper = operStack.pop();
num1 = numStack.pop();
num2 = numStack.pop();
res = calcalator(num1,num2,oper);
numStack.pushOne(res);
operStack.pushOne(ch);
}else {
operStack.pushOne(ch);
}
}
}else {
String keepNum1 = expresion.substring(index,index+1);
/*循环内 判断 index 下一个指针中指的是啥，分三种情况 1，是空（index指向的字符已经是最后一个字符了）
2，是操作符，
3，是数字
*/
while (true){
//1，2，两种情况
if(index+1 == expresion.length() || isOper(expresion.charAt(index+1)))
break;
//3，中情况，index 指针往后移动
keepNum1+= expresion.substring(++index,index+1);
}
numStack.pushOne(Integer.valueOf(keepNum1));
}
index++;
}
while (!operStack.isEmpty()){
oper = operStack.pop();
num1 = numStack.pop();
num2 = numStack.pop();
res = calcalator(num1,num2,oper);
numStack.pushOne(res);
}
System.out.println(numStack.pop());
}
/*
* 比较操作符的优先级
* @author cjj_1
* @date 2020-08-06 11:50:31
* @param oper
* @return
**/
public static int priority(int oper){
if(oper == '*' || oper == '/')
return 1;
else if(oper == '+' || oper == '-')
return 0;
else
return -1;
}
/*
* 运算数据
* @author cjj_1
* @date 2020-08-06 11:51:24
* @param num1
* @param num2
* @param oper
* @return
**/
public static int calcalator(int num1,int num2,int oper){
int res=0;
switch (oper){
case '*':
res = num2*num1;
break;
case '/':
res = num2/num1;
break;
case '+':
res = num2+num1;
break;
case '-':
res = num2-num1;
break;
default:
res=-1;
break;
}
return res;
}
public static Boolean isOper(int oper){
return oper=='*' || oper=='/'||oper=='+'|| oper=='-';
}
}
/**
* 栈
*/
class Stack4Calcalator {
int[] stack;
int maxSize;
int pop;
public Stack4Calcalator(int maxsize){
this.pop = -1;
this.maxSize = maxsize;
this.stack = new int[maxsize];
}
public boolean isFull()
{
if(pop == maxSize-1)
return Boolean.TRUE;
return Boolean.FALSE;
}
public boolean isEmpty()
{
if(pop == -1)
return Boolean.TRUE;
return Boolean.FALSE;
}
public void pushOne(int num){
if(isFull()){
return;
}
pop++;
stack[pop]= num;
}
//出栈
public int pop(){
if(isEmpty())
return -1;
return stack[pop--];
}
//获取栈顶的值
public int picck(){
if(isEmpty())
return -1;
return stack[pop];
}
}
转载于：https://blog.csdn.net/weixin_40128696/article/details/107856835
