LeetCode 227 - Basic Calculator II

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.

You may assume that the given expression is always valid.

Some examples:

"3+2*2" = 7
" 3/2 " = 1
" 3+5 / 2 " = 5

 

Note: Do not use the eval built-in library function.

和本博客下面连接的题目一模一样，这里再写一遍。

http://yuanhsh.iteye.com/blog/2194524

 

public int calculate(String s) {
    String[] arr = s.split("[\\+\\-\\*\\/]");
    String[] ops = s.split("\\d+");
    int n = arr.length;
    int[] nums = new int[n];
    for(int i=0; i<n; i++) {
        nums[i] = Integer.parseInt(arr[i].trim());
    }
    for(int i=1; i<n; i++) {
        char op = ops[i].trim().charAt(0);
        if(op == '-') {
            nums[i] = -nums[i];
        } else if(op == '*') {
            nums[i] = nums[i-1]*nums[i];
            nums[i-1] = 0;
        } else if(op == '/') {
            nums[i] = nums[i-1]/nums[i];
            nums[i-1] = 0;
        }
    }
    int sum = 0;
    for(int num:nums) sum += num;
    return sum;
}