Merge pull request #1091 from MaxMaxner/1052-find-three-largest-Integer-js

resolves ticket #1052 find three largest Integer in Javascript

Author: akgmage

Arrays/find_three_largest_integers.js

@@ -0,0 +1,81 @@
+/*
+Write a function that takes in an array of at least three integers and, 
+without sorting the input array, returns a sorted array of the three largest integers in the input array.
+
+
+Approach:
+
+Before implementing the task logic the array will be checked to see if it meets the criteria.
+Here the input array will be checked to see if it´s at least 3 elements big and if it
+only contains integers.
+
+After that the logic is implemented.
+Because the given array should not be sorted for this task, the used logic works as following:
+1. Initialize a result array with 3 values, each of these 3 is initialized as -Infinity
+2. Check if first element of array is bigger than the third result value
+    2.1 If value is bigger set new value (will be true for the first check as initialized with -Infinity)
+    2.2 shift current numbers in result array
+    2.3 checks if element is bigger than value 2, and also value 1 - following above logic
+3. Sorty the result array in descending order and console logs the result.
+*/
+
+function findThreeLargestInteger(array) {
+
+    /************************************************************************
+     *        This block checks if given array matches the criteria         *
+    ************************************************************************/
+    let arrayLength = 0;
+    let onlyIntegers = true;
+    // iterate over given array and check each element 
+    array.forEach(element => {
+        // is element an integer
+        if (!Number.isInteger(element)) {
+            onlyIntegers = false;
+        }
+        // count length of array
+        arrayLength++;
+    });
+
+
+    /************************************************************************
+     *                    Implementing the task logic                       *
+    ************************************************************************/
+    if (onlyIntegers && arrayLength >= 3) {
+        // initialize result array with -Infinite
+        let result = [-Infinity, -Infinity, -Infinity];
+
+        // Loop through the input array
+        for (const num of array) {
+            // Check if the current number is larger than the third largest number
+            if (num > result[2]) {
+                // Shift the current numbers down the result array
+                result[0] = result[1];
+                result[1] = result[2];
+                result[2] = num;
+            } else if (num > result[1]) {
+                // Shift the current numbers down the result array
+                result[0] = result[1];
+                result[1] = num;
+            } else if (num > result[0]) {
+                // Shift the current number down the result array
+                result[0] = num;
+            }
+        }
+        // sorts the result in descending order (big to small)
+        result.sort(function (a, b) { return b - a });
+        console.log(result);
+
+    } else {
+        console.log("The passed array does not match the expected criteria.");
+    }
+
+}
+
+const testArray = [5, -3, 5, 100, 3, 55, 999, -18];
+const functionCheck = findThreeLargestInteger(testArray); // prints [999, 100, 55] to console
+
+const arrayToShort = [100, 999];
+const unctionCheck1 = findThreeLargestInteger(arrayToShort); // prints "The passed array does not match the expected criteria." to console
+
+const arrayNoInt = [100, 999, 8.5];
+const unctionCheck2 = findThreeLargestInteger(arrayNoInt); // prints "The passed array does not match the expected criteria." to console