$$config title: 스택 문자열 계산 keywords: - java $$ # 코드 ```java package stackCalc.exam; import java.util.*; public class Calc { public double calc(String s) { ArrayList postFix = toPoistFix(s); Stack stack = new Stack<>(); double front, back; for (int i = 0; i < postFix.size(); i++) { switch (postFix.get(i)) { case "+": back = Double.parseDouble(stack.pop()); front = Double.parseDouble(stack.pop()); stack.push((front + back) + ""); break; case "-": back = Double.parseDouble(stack.pop()); front = Double.parseDouble(stack.pop()); stack.push((front - back) + ""); break; case "*": back = Double.parseDouble(stack.pop()); front = Double.parseDouble(stack.pop()); stack.push((front * back) + ""); break; case "/": back = Double.parseDouble(stack.pop()); front = Double.parseDouble(stack.pop()); stack.push((front / back) + ""); break; default: stack.push(postFix.get(i)); } } System.out.printf("%.0f", Double.parseDouble(stack.pop())); return 0; } public int getPriority(String str) { switch (str) { case "(": case ")": return 0; case "+": case "-": return 1; case "*": case "/": return 2; } return -1; } public ArrayList toPoistFix(String str) { ArrayList result = new ArrayList<>(); str=str.replace("(", "( "); str=str.replace(")", " )"); str=str.replace("+", " + "); str=str.replace("-", " - "); str=str.replace("/", " / "); str=str.replace("*", " * "); str=str.replace(" "," "); String[] calcTarget = str.split(" "); Stack stack = new Stack<>(); String forPrint = ""; for (int i = 0; i < calcTarget.length; i++) { switch (calcTarget[i]) { case "(": stack.push(calcTarget[i]); break; case ")": forPrint = stack.pop(); while (!forPrint.equals("(")) { result.add(forPrint); forPrint = stack.pop(); } break; case "+": case "-": case "*": case "/": while (!stack.isEmpty() && getPriority(calcTarget[i]) <= getPriority(stack.peek())) { forPrint = stack.pop(); result.add(forPrint); } stack.push(calcTarget[i]); break; case " ": break; default: result.add(calcTarget[i]); } } while (!stack.isEmpty()) { forPrint = stack.pop(); result.add(forPrint); } System.out.println(result); return result; } } ```

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