實作按下 % 要怎麼處理

AndroidCalculator/Calculator.swift

@@ -72,6 +72,16 @@ class Calculator {
         formula.append("-" + formula.popLast()!)
       }
       
+    case "%":
+      if ["+", "-", "×", "÷"].firstIndex(of: formula.last!) != nil {
+        return
+      }
+      if (Double(formula.last!)! / 100).truncatingRemainder(dividingBy: 1) != 0 {
+        formula.append(String(Double(formula.popLast()!)! / 100))
+      } else {
+        formula.append(String(Int(formula.popLast()!)! / 100))
+      }
+      
     default:
       print(formula)
     }