feat : 인프런 3주차 39 후위식 연산

Author: cyeji

src/main/java/sgyj/inflearn/yeji/week4/Solution39.java

@@ -0,0 +1,48 @@
+package sgyj.inflearn.yeji.week4;
+
+import java.util.Scanner;
+import java.util.Stack;
+
+
+class Solution39{
+    // 후위식 연산
+    public static int solution(String[] input){
+        Stack<Integer> stack = new Stack();
+
+        for(String i : input){
+            if(isNumeric(i)){
+                stack.push(Integer.parseInt(i));
+            }else{
+                stack.push(checkNum(stack.pop(),stack.pop(), i));
+            }
+        }
+        return stack.pop();
+    }
+
+    public static boolean isNumeric(String i){
+        try{
+            Integer.parseInt(i);
+            return true;
+        }catch(NumberFormatException e){
+            return false;
+        }
+    }
+
+    public static int checkNum(int stack1, int stack2, String target){
+        if(target.equals("+")){
+            return stack2+stack1;
+        }else if(target.equals("-")){
+            return stack2-stack1;
+        }else if(target.equals("*")){
+            return stack2*stack1;
+        }
+        return stack2/stack1;
+    }
+
+    public static void main(String[] args){
+        Scanner sc = new Scanner(System.in);
+        String input = sc.nextLine();
+        System.out.println(solution(input.split("")));
+    }
+
+}