本文主要是介绍Basic Calculator,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
题意:
写一个简单的计算器,此计算器只有加法,减法及括号操作
分析:
开两个栈,一个村操作数,一个村操作符,其中+与-同级,当一个操作符要进栈时,判断操作符栈顶元素,若是同级,则让操作数栈出栈两个数,操作符栈出栈栈顶元素,然后将计算出的结果存入操作数栈,待进栈操作符进栈;当遇到左括号时,果断进栈,遇到右括号,则先计算括号中的结果,然后对应的左括号出栈;
最终使得操作符栈为空,计算出的结果即为最后结果
参考代码:
http://www.programcreek.com/2014/06/leetcode-basic-calculator-java/
写好长啊!!!
public class Solution {public int calculate(String s) {// delte white spacess = s.replaceAll(" ", "");Stack<String> stack = new Stack<String>();char[] arr = s.toCharArray();StringBuilder sb = new StringBuilder();for (int i = 0; i < arr.length; i++) {if (arr[i] == ' ')continue;if (arr[i] >= '0' && arr[i] <= '9') {sb.append(arr[i]);if (i == arr.length - 1) {stack.push(sb.toString());}} else {if (sb.length() > 0) {stack.push(sb.toString());sb = new StringBuilder();}if (arr[i] != ')') {stack.push(new String(new char[] { arr[i] }));} else {// when meet ')', pop and calculateArrayList<String> t = new ArrayList<String>();while (!stack.isEmpty()) {String top = stack.pop();if (top.equals("(")) {break;} else {t.add(0, top);}}int temp = 0;if (t.size() == 1) {temp = Integer.valueOf(t.get(0));} else {for (int j = t.size() - 1; j > 0; j = j - 2) {if (t.get(j - 1).equals("-")) {temp += 0 - Integer.valueOf(t.get(j));} else {temp += Integer.valueOf(t.get(j));}}temp += Integer.valueOf(t.get(0));}stack.push(String.valueOf(temp));}}}ArrayList<String> t = new ArrayList<String>();while (!stack.isEmpty()) {String elem = stack.pop();t.add(0, elem);}int temp = 0;for (int i = t.size() - 1; i > 0; i = i - 2) {if (t.get(i - 1).equals("-")) {temp += 0 - Integer.valueOf(t.get(i));} else {temp += Integer.valueOf(t.get(i));}}temp += Integer.valueOf(t.get(0));return temp;
}
}
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