1106. Parsing A Boolean Expression

Return the result of evaluating a given boolean expression, represented as a string.

An expression can either be:

• "t", evaluating to True;
• "f", evaluating to False;
• "!(expr)", evaluating to the logical NOT of the inner expression expr;
• "&(expr1,expr2,...)", evaluating to the logical AND of 2 or more inner expressions expr1, expr2, ...;
• "|(expr1,expr2,...)", evaluating to the logical OR of 2 or more inner expressions expr1, expr2, ...

Example 1:

Input: expression = "!(f)"
Output: true

Example 2:

Input: expression = "|(f,t)"
Output: true

Example 3:

Input: expression = "&(t,f)"
Output: false

Example 4:

Input: expression = "|(&(t,f,t),!(t))"
Output: false

Constraints:

• 1 <= expression.length <= 20000
• expression[i] consists of characters in {'(', ')', '&', '|', '!', 't', 'f', ','}.
• expression is a valid expression representing a boolean, as given in the description.

# @lc code=start
using LeetCode

function parse_bool_expr(expr::String)
    operations = Char[]
    operands = Char[]
    for ch in expr
        if ch == '!' || ch == '&' || ch == '|'
            push!(operations, ch)
        elseif ch == ')'
            cur_oprs = Char[]
            while operands[end] != '('
                push!(cur_oprs, pop!(operands))
            end
            pop!(operands)
            op = pop!(operations)
            rs = true
            if op == '|'
                rs = any(==('t'), cur_oprs)
            elseif op == '&'
                rs = all(==('t'), cur_oprs)
            else
                rs = cur_oprs[1] != 't'
            end
            push!(operands, rs ? 't' : 'f')
        elseif ch != ','
            push!(operands, ch)
        end
    end
    return operands[1] == 't' ? true : false
end
# @lc code=end

parse_bool_expr (generic function with 1 method)

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