coding-Interview/BasicCalculatorIII.java at master · arjunmullick/coding-Interview · GitHub

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package com.leetcode;

import java.util.LinkedList;

import java.util.Queue;

import java.util.Stack;

public class BasicCalculatorIII {

//https://leetcode.com/problems/basic-calculator-iii/

class Solution {

public int calculate(String s) {

Queue<Character> queue = new LinkedList<>();

for(char c : s.toCharArray()){

queue.offer(c);

}

queue.offer('+');

return calculateQueue(queue);

}

public int calculateQueue(Queue<Character> queue){

int result = 0;

int op = '+';

int num = 0;

Stack<Integer> stack = new Stack<>();

while(queue.size() > 0){

char ch = queue.poll();

if(ch == ' ') continue;

if(Character.isDigit(ch)){

num = num * 10 + ch -'0';

}else if(ch == '('){

num = calculateQueue(queue);//caclulate and update num

}else if(!Character.isDigit(ch)){

if(op == '+'){

stack.push(num);

}else if(op == '-'){

stack.push(-num);

}else if(op == '*'){

stack.push(stack.pop() * num);

}else if(op == '/'){

stack.push(stack.pop() / num);

}

op = ch;

num = 0;

}

if(ch == ')'){

break;

}

while(stack.size() > 0){

result += stack.pop();

}

return result;

}

coding-Interview/BasicCalculatorIII.java at master · arjunmullick/coding-Interview · GitHub

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