Created
January 30, 2018 09:06
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簡易版本的後序計算程式,應用堆疊(Stack)資料結構。
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import java.util.Arrays; | |
import java.util.Stack; | |
import java.util.regex.Pattern; | |
/* | |
* 簡易版本的後序計算程式,應用堆疊(Stack)資料結構。 | |
*/ | |
public class StackExample { | |
public static void main(String[] args) { | |
/* | |
* 中序:((1+2)*(3+4)) | |
* 後序:12+34+* | |
* 計算結果:21 | |
*/ | |
calculatorPostfix(new String[] { "1", "2", "+", "3", "4", "+", "*" }); | |
} | |
/** | |
* 以後序進行計算 | |
* | |
* @param postfix | |
*/ | |
private static void calculatorPostfix(String[] postfix) { | |
Stack<String> stack = new Stack<String>(); | |
for (int i = 0; i < postfix.length; i++) { | |
String token = String.valueOf(postfix[i]); | |
boolean operand = Pattern.matches("[0-9]", token); | |
if (operand) { | |
stack.push(token); | |
continue; | |
} | |
String x = stack.pop(); | |
String y = stack.pop(); | |
if ("+".equals(token)) { | |
String z = String.valueOf(Integer.parseInt(x) + Integer.parseInt(y)); | |
stack.push(z); | |
} else if ("-".equals(token)) { | |
String z = String.valueOf(Integer.parseInt(x) - Integer.parseInt(y)); | |
stack.push(z); | |
} else if ("*".equals(token)) { | |
String z = String.valueOf(Integer.parseInt(x) * Integer.parseInt(y)); | |
stack.push(z); | |
} else if ("/".equals(token)) { | |
String z = String.valueOf(Integer.parseInt(x) / Integer.parseInt(y)); | |
stack.push(z); | |
} | |
} | |
System.out.println("input: " + Arrays.toString(postfix)); | |
System.out.println("output: " + stack.pop()); | |
} | |
} |
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