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March 18, 2021 23:33
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| import java.util.* | |
| fun main(args: Array<String>) { | |
| val scanner = Scanner(System.`in`) | |
| val operators = listOf('^', '*', '/', '+', '-', '>', '<', '=', '#', '.', '|') | |
| val operands = "[a-zA-Z0-9]+".toRegex() | |
| abstract class Expression | |
| class OperandExpression(val left: Expression, val operator: Char, val right: Expression) : Expression() { | |
| override fun toString() = "exp($left $operator $right)" | |
| } | |
| class ConstantExpression(val value: String) : Expression() { | |
| override fun toString() = value | |
| } | |
| fun parseExpression(expression: String) : Expression { | |
| return if (expression.matches(operands)) { | |
| ConstantExpression(expression) | |
| } else { | |
| if (expression.startsWith('(') && expression.endsWith(')')) { | |
| val startIndex = expression.indexOf('(') | |
| val (_, endIndex) = expression | |
| .substring(startIndex) | |
| .toCharArray() | |
| .asList() | |
| .foldRightIndexed(1 to -1) { index, char, acc -> | |
| val (depth) = acc | |
| if (depth > 0) { | |
| when (char) { | |
| '(' -> depth+1 to index | |
| ')' -> depth-1 to index | |
| else -> depth to index | |
| } | |
| } else acc | |
| } | |
| parseExpression(expression.substring(startIndex+1, startIndex+endIndex)) | |
| } else { | |
| var depth = 0 | |
| val index = expression.mapIndexedNotNull { index, it -> | |
| if (it == '(') depth++ | |
| if (it == ')') depth-- | |
| if (depth == 0) { | |
| val operator = operators.firstOrNull(it::equals) | |
| if (operator != null) { | |
| return@mapIndexedNotNull index as Int? | |
| } | |
| } | |
| return@mapIndexedNotNull null as Int? | |
| }.maxByOrNull { operators.indexOf(expression[it]) } ?: error("Syntactical Error") | |
| val left = expression.take(index) | |
| val right = expression.substring(index + 1) | |
| if (left.isBlank() || right.isBlank()) { | |
| error("Syntactical Error") | |
| } | |
| OperandExpression(parseExpression(left), expression[index], parseExpression(right)) | |
| } | |
| } | |
| } | |
| while (scanner.hasNext()) { | |
| val expression = scanner.nextLine().replace(" ", "") | |
| try { | |
| if (!expression.all { it == '(' || it == ')' || it in operators || it.toString().matches(operands) }) { | |
| error("Lexical Error") | |
| } | |
| println(parseExpression(expression)) | |
| } catch (e: IllegalStateException) { | |
| println(e.message) | |
| } | |
| } | |
| } |
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