227. Basic Calculator II

Given a string s which represents an expression, evaluate this expression and return its value.

The integer division should truncate toward zero.

Example 1:

Input: s = "3+2*2"
Output: 7

Example 2:

Input: s = " 3/2 "
Output: 1

Example 3:

Input: s = " 3+5 / 2 "
Output: 5

Constraints:

• 1 <= s.length <= 3 * 105
• s consists of integers and operators ('+', '-', '*', '/') separated by some number of spaces.
• s represents a valid expression.
• All the integers in the expression are non-negative integers in the range [0, 231 - 1].
• The answer is guaranteed to fit in a 32-bit integer.

# @lc code=start
using LeetCode

function calculate_ii(s::String)::Int
    num, stk, sign = 0, Int64[], '+'

    for (i, c) in enumerate(s)
        isdigit(c) && (num = 10 * num + parse(Int, c))
        if c in ['-', '+', '/', '*'] || i == length(s)
            if sign == '+'
                push!(stk, num)
            elseif sign == '-'
                push!(stk, -num)
            elseif sign == '*'
                push!(stk, pop!(stk) * num)
            elseif sign == '/'
                push!(stk, pop!(stk) ÷ num)
            end

            num = 0
            sign = c
        end
    end

    return sum(stk)
end

# @lc code=end

calculate_ii (generic function with 1 method)

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