Solution.js code written #Github-Externship-Assignment@kLamda

Solution.js

@@ -1 +1,66 @@
 // Write your code here
+class FixEquation {
+
+    findMissingDigit(input) {
+        //Replacing multiple spaces
+        input = input.replace( /  +/g, ' ' ); 
+        //Splitting the equation into array of characters
+        var characters = input.split(" "); 
+        //Assigning missingIndex as -1
+        var missingIndex = -1;
+        //value array declaration
+        const value = new Array();
+
+        for(var i = 0; i < characters.length; i++) {
+            if(characters[i] !== '+' && characters[i] !== '*' && characters[i] !== '=') {
+                if(characters[i].includes('?')) {
+                    missingIndex = i; 
+                    value.push(characters[i]);
+                }
+                else {
+                    value.push(parseInt(characters[i]));
+                }
+            }
+        }
+
+        //Parse A, B, C, D values
+        var [A, B, C, D] = value;
+
+        //Initialize sol variable
+        var sol = 0;
+        switch(missingIndex) {
+            case 0:
+                sol = (D - C) / B;
+                break;
+            case 2:
+                sol = (D - C) / A;
+                break;
+            case 4:
+                sol = D - (A * B);
+                break;
+            default:
+                sol = (A * B) + C;
+                break;
+        }
+
+        //Return Final Values       
+        if(sol == parseInt(characters[missingIndex].replace('?', '')) || (Number(sol) == sol && sol % 1 !== 0) || sol < 0) {
+            return -1;
+        }
+        return parseInt(sol.toString()[characters[missingIndex].indexOf('?')]) || -1;
+    }
+}
+
+//TestCases
+var Testcases = [
+    '5? * 57 + 4 = 3196',
+    '26 * ?7 + 4 = 1486',
+    '42 * 9 + 78 = 4?6',
+    '22 * 87 + ?3 = 1927',
+    '?2 * 97 + 4 = 74',
+]
+
+//Run TestCases
+Testcases.forEach(item => {
+    console.log(new FixEquation().findMissingDigit(item))
+});