package com.ecust.jvm3;
import java.util.HashMap;
import java.util.Stack;
public class InfixExpr2 {
public static enum TypeToken {
add('+',0),substruct('-',1),devide('/',3),plus('*',2);
TypeToken(char token, Integer priority) {
this.token = token;
this.priority = priority;
}
private char token;
private Integer priority;
}
String expr = null;
public InfixExpr2(String expr) {
this.expr = expr;
}
//3*20+12*5-40/2
public Double evaluate() {
HashMap<String, Integer> map = new HashMap<>();
map.put("+",0);
map.put("-",1);
map.put("/",3);
map.put("*",2);
Stack tokenStack = new Stack();
Stack numStack = new Stack();
char[] chars = expr.toCharArray();
boolean isNem = true;
for (int i = 0; i < expr.length(); i++) {
String token = (expr.charAt(i)) + "";
Integer priprity = map.get(token);
if (priprity != null) {
//表示是运算符
if (!tokenStack.isEmpty() && priprity < map.get(tokenStack.peek())) {
Float num2 = Float.valueOf(numStack.pop().toString());
Float num1 = Float.valueOf(numStack.pop().toString());
String pop = tokenStack.pop()+"";
if (pop.equals("-")) {
numStack.push(num1 - num2);
} else if (pop.equals("*")){
numStack.push(num1 * num2);
} else if (pop.equals("/")){
numStack.push(num1 / num2);
} else {
throw new RuntimeException();
}
}
tokenStack.push(token);
isNem = true;
} else if(token.matches("\\d{1}")) {
//表示是数字
if (isNem) {
numStack.push(token);
} else {
numStack.push(numStack.pop().toString() + token);
}
isNem = false;
} else {
throw new RuntimeException();
}
}
while (!tokenStack.isEmpty()) {
System.out.println(tokenStack.size());
if (tokenStack.peek().equals("+")) {
Float num2 = Float.valueOf(numStack.pop().toString());
Float num1 = Float.valueOf(numStack.pop().toString());
numStack.push(num1+num2+"");
} else if (tokenStack.peek().equals("-")) {
Float num2 = Float.valueOf(numStack.pop().toString());
Float num1 = Float.valueOf(numStack.pop().toString());
numStack.push(num1-num2+"");
} else if (tokenStack.peek().equals("/")) {
Float num2 = Float.valueOf(numStack.pop().toString());
Float num1 = Float.valueOf(numStack.pop().toString());
numStack.push(num1/num2+"");
} else if (tokenStack.peek().equals("*")) {
Float num2 = Float.valueOf(numStack.pop().toString());
Float num1 = Float.valueOf(numStack.pop().toString());
numStack.push(num1*num2+"");
} else {
throw new RuntimeException();
}
tokenStack.pop();
}
return Double.valueOf(numStack.pop().toString());
}
}