/* #Problem Task A list of strings is given and each string will do following tasks: x is an integer; enter a new x score. "+" - Add the previous two scores together to create a new score. There will always be at least two previous scores. "D" - Make a new score that is twice as high as the previous one. There will almost certainly be a previous score. "R" - Remove the previous score from the record by invalidating it. There will almost certainly be a previous score. Return the total of all the records' scores. Input: ops = ["7","-8","9","R","D","10","+","+"] Output: -9 Explanation: "7" - Increase the record by 7, making it [7]. "-8" - Increase the record by -8, making it [7, -8]. "9" - Increase the record by 9, making it [7, -8, 9]. "R" - Discard the previous score and replace it with [7, -8]. "D" - To the record, add 2* -8 = -16, making the record [7, -8, -16]. "10" - Increase the record by one, making it [7, -8, -16, 10]. "+" - Make the record [7, -8, -16, 10, -6 ] by adding -16 + 10 = -6. "+" - Make the record [7, -8, -16, 10, -6, 4] by adding 10+ -6 = 4. 7 + -8 + -16 + 10 + -6 + 4 = -9 is the total. */ // existing Array const ops = ['7', '-8', '9', 'R', 'D', '10', '+', '+']; // update value from the loop of Array(ops) let updateValues = []; // traversing the Array(ops) and applying logics for (let i = 0; i < ops.length; i++) { // conditions & checkings // check the string contains number or not if (/^[-+]?[0-9]\d*(\.\d+)?$/.test(ops[i])) { const parseToInt = parseInt(ops[i]); updateValues.push(parseToInt); } // discard the previous score and replace else if (ops[i] === 'R') { updateValues.pop(); } // multiply the last element of the Array(updateValues) else if (ops[i] === 'D') { const multiplyTheValue = updateValues[updateValues.length - 1] * 2; updateValues.push(multiplyTheValue); } // make the record by adding [-16 + 10] & [10 + -6] else if (ops[i] === '+') { updateValues.push( updateValues[updateValues.length - 2] + updateValues[updateValues.length - 1] ); } } // counting the final output const finalResult = updateValues.reduce((a, b) => a + b, 0); console.log(finalResult); // Output = -9