fixed functions within mini-challenges

src/brackets/index.js

@@ -4,6 +4,41 @@
  * @param {string} str The string of brackets.
  * @returns {"valid" | "invalid"} Whether or not the string is valid.
  */
-function isValid(str) {}
+function isValid(str) {
+
+    const count = [];
+
+    //  create a correct pairing with key:value pairs
+    const correctPairing = {
+        '(': ')',
+        '[': ']',
+        '{': '}',
+    };
+
+        for (let char of str) {
+
+            // iterate through the characters in the string
+          if (char in correctPairing) {
+
+            // push consecutive opening brackets to the count variable
+
+            count.push(char);
+          } else if (Object.values(correctPairing).includes(char)) {
+
+            // remove most current occurence of opening brackets (key) if a closing bracket (value) is met
+
+            const lastOpeningBracket = count.pop();
+
+            //  if the popped value does not match the key, return invalid;
+
+            if (!lastOpeningBracket || correctPairing[lastOpeningBracket] !== char) {
+              return "invalid";
+            }
+          }
+        }
+        // check the length of remaining characters in the count variable, if 0, all brackets have succesfully paired, else it is invalid
+
+    return count.length === 0 ? "valid" : "invalid";    
+}
 
 module.exports = isValid;

src/roman-numerals/index.js

@@ -4,6 +4,27 @@
  * @param {string} roman The all-caps Roman numeral between 1 and 3999 (inclusive).
  * @returns {number} The decimal equivalent.
  */
-function romanToDecimal(roman) {}
+function romanToDecimal(roman) {
+    const romanToDecimal = {
+        I: 1,
+        V: 5,
+        X: 10,
+        L: 50,
+        C: 100,
+        D: 500,
+        M: 1000,
+    };
+
+    let total = 0;
+
+    for (let i = 0; i < roman.length; i++) {
+        const currentChar = romanToDecimal[roman[i]];
+        const nextChar = romanToDecimal[roman[i + 1]];
+
+        total += nextChar && nextChar > currentChar ? -currentChar : currentChar;
+    }
+
+    return total;    
+}
 
 module.exports = romanToDecimal;

src/transpose/index.js

@@ -4,6 +4,24 @@
  * @param {number[]} array The array to transpose
  * @returns {number[]} The transposed array
  */
-function transpose(array) {}
+function transpose(array) {
+
+        //  create new Parent and Child Arrays
+        const newRowLength = array.length;
+        const newColLength = array[0].length;
+
+        const transposedArray = [];
+
+        // iterate over array to create new rows and column
+        for (let col = 0; col < newColLength; col++) {
+          const newRow = [];
+          for (let row = 0; row < newRowLength; row++) {
+            newRow.push(array[row][col]);
+          }
+          transposedArray.push(newRow);
+        }
+
+    return transposedArray;
+}
 
 module.exports = transpose;