[백준 1935] 후위 표기식2 - 자료구조

Author: jcw1031

chanwoo/week02/후위표기식2.java

@@ -0,0 +1,78 @@
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.Stack;
+
+/**
+ * 1935번
+ */
+public class Main {
+
+    private static final Stack<Character> operationStack = new Stack<>();
+    private static final Stack<Double> operandStack = new Stack<>();
+    public static final int CHARACTER_A_ASCII_CODE = 65;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+
+        int n = Integer.parseInt(br.readLine());
+        int[] value = new int[n];
+        String postfixExpression = br.readLine();
+
+        for (int i = 0; i < n; i++) {
+            value[i] = Integer.parseInt(br.readLine());
+        }
+
+        for (int i = 0; i < postfixExpression.length(); i++) {
+            char bitOfExpression = postfixExpression.charAt(i);
+            if (isOperation(bitOfExpression)) {
+                operationStack.push(bitOfExpression);
+                calculate();
+                continue;
+            }
+            operandStack.push((double) value[bitOfExpression - CHARACTER_A_ASCII_CODE]);
+        }
+
+        Double result = operandStack.pop();
+        bw.write(String.format("%.2f", result));
+        bw.flush();
+        bw.close();
+    }
+
+    public static boolean isOperation(char bit) {
+        if (Character.isAlphabetic(bit)) {
+            return false;
+        }
+        return true;
+    }
+
+    public static void calculate() {
+        Double rightOperand = operandStack.pop();
+        Double leftOperand = operandStack.pop();
+        Character operation = operationStack.pop();
+
+        double result = operate(leftOperand, rightOperand, operation);
+        operandStack.push(result);
+    }
+
+    private static double operate(Double leftOperand, Double rightOperand, Character operation) {
+        switch (operation) {
+            case '+': {
+                return leftOperand + rightOperand;
+            }
+            case '-': {
+                return leftOperand - rightOperand;
+            }
+            case '*': {
+                return leftOperand * rightOperand;
+            }
+            case '/': {
+                return leftOperand / rightOperand;
+            }
+        }
+        return 0;
+    }
+}