[2020kakao(intern)-p2] 수식 최대화

Author: Seogeurim

README.md

@@ -516,3 +516,4 @@
 |  #  |  ☆  | Problem                                       | Note |
 | :-: | :-: | :-------------------------------------------- | :--- |
 | 01  |     | [키패드 누르기](./src/_2020_카카오_인턴십/P1) |      |
+| 02  |     | [수식 최대화](./src/_2020_카카오_인턴십/P2) |      |

src/_2020_카카오_인턴십/P2/Main.java

@@ -0,0 +1,70 @@
+package _2020_카카오_인턴십.P2;
+
+import java.util.*;
+
+public class Main {
+
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.solution("100-200*300-500+20")); // 60420
+        System.out.println(sol.solution("50*6-3*2")); // 300
+    }
+}
+
+class Solution {
+
+    char[][] opCases = {
+            {'+', '-', '*'},
+            {'+', '*', '-'},
+            {'-', '+', '*'},
+            {'-', '*', '+'},
+            {'*', '+', '-'},
+            {'*', '-', '+'}
+    };
+
+    public long solution(String expression) {
+
+        List<Long> numList = new ArrayList<>();
+        List<Character> opList = new ArrayList<>();
+
+        int idx = 0, n = expression.length();
+        while (idx < n) {
+            StringBuilder num = new StringBuilder();
+            while (idx < n && !isOp(expression.charAt(idx))) {
+                num.append(expression.charAt(idx++));
+            }
+            numList.add(Long.parseLong(num.toString()));
+            if (idx < n) opList.add(expression.charAt(idx++));
+        }
+
+        long ans = 0;
+        for (char[] op : opCases) {
+            List<Long> nums = new ArrayList<>(numList);
+            List<Character> ops = new ArrayList<>(opList);
+
+            for (int i = 0; i < 3; i++) {
+                int ofs;
+                while ((ofs = ops.indexOf(op[i])) >= 0) {
+                    nums.add(ofs, calc(op[i], nums.get(ofs), nums.get(ofs+1)));
+                    nums.remove(ofs+1);
+                    nums.remove(ofs+1);
+                    ops.remove(ofs);
+                }
+            }
+
+            ans = Math.max(ans, Math.abs(nums.get(0)));
+        }
+
+        return ans;
+    }
+
+    private boolean isOp(char c) {
+        return c == '+' || c == '*' || c == '-';
+    }
+
+    private long calc(char op, long a, long b) {
+        if (op == '*') return a*b;
+        else if (op == '+') return a+b;
+        else return a-b;
+    }
+}

src/_2020_카카오_인턴십/P2/README.md

@@ -0,0 +1,3 @@
+## [2020 카카오 인턴십] 수식 최대화
+
+![image](https://user-images.githubusercontent.com/22045163/116247404-c74bad00-a7a5-11eb-8f81-d1931eae7898.png)