221 lines
7.1 KiB
Markdown
221 lines
7.1 KiB
Markdown
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---
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title: Cash Register Challenge on freeCodeCamp
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tags: [webdev, javascript, freecodecamp]
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category: programming
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---
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I've been (slowly) working through the JavaScript module on [freeCodeCamp](https://freecodecamp.org) for a while now, and have recently been doing the certificate challenges. The last of which is the "Cash Register" challenge where you are to write a function that takes a price, a payment amount and an array that contains the cash in the drawer.
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I found a couple of things strange about the challenge
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| Currency Unit | Amount |
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| ------------------- | ------------------ |
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| Penny | $0.01 (PENNY) |
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| Nickel | $0.05 (NICKEL) |
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| Dime | $0.1 (DIME) |
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| Quarter | $0.25 (QUARTER) |
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| Dollar | $1 (ONE) |
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| Five Dollars | $5 (FIVE) |
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| Ten Dollars | $10 (TEN) |
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| Twenty Dollars | $20 (TWENTY) |
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| One-hundred Dollars | $100 (ONE HUNDRED) |
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Example of the cash in drawer array:
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```javascript
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[
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["PENNY", 1.01],
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["NICKEL", 2.05],
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["DIME", 3.1],
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["QUARTER", 4.25],
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["ONE", 90],
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["FIVE", 55],
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["TEN", 20],
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["TWENTY", 60],
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["ONE HUNDRED", 100]
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]
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```
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Sample input to function,
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```javascript
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checkCashRegister(3.26, 100, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]])
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```
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and the expected return object
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```javascript
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{status: "OPEN", change: [["TWENTY", 60], ["TEN", 20], ["FIVE", 15], ["ONE", 1], ["QUARTER", 0.5], ["DIME", 0.2], ["PENNY", 0.04]]}
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```
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Why is this weird? Well it was drilled into me back in college (1991/1992), to NEVER use floating point values for currency. Its inpercise (especially in JavaScript) and this challenge just doubles down on it.
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I'd much rather see that there are 101 PENNIES that 1.01 in PENNIES. I find it faster to say give 4 pennies as change than 0.04 pennies.
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Final **solution**
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```javascript
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function checkCashRegister(price, cash, cid) {
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/*
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First step, adjust amounts into pennies.
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Learnt long ago to never use floats
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for currency.
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*/
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let adjustmentAmount = 100;
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let adjustedPrice = price * adjustmentAmount;
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let adjustedCashGiven = cash * adjustmentAmount;
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// Reverse cid, need to make new array as using = is just a reference
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let cashInDrawer = Array.from(cid);
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cashInDrawer.reverse();
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// total of all the cash in drawer
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let totalCashInDrawer = 0;
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// in the array the denomination comes in an array with two parts, name and value
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const availableCashInDrawer = cashInDrawer.map((denomination) => {
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const adjustedAmount = Math.round(denomination[1] * adjustmentAmount);
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totalCashInDrawer += adjustedAmount;
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return [denomination[0], adjustedAmount];
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});
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// console.log(
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// "Total Cash in Drawer",
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// totalCashInDrawer,
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// " -- $",
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// totalCashInDrawer / adjustmentAmount
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// );
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let currencyValues = {
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"ONE HUNDRED": 10000,
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TWENTY: 2000,
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TEN: 1000,
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FIVE: 500,
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ONE: 100,
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QUARTER: 25,
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DIME: 10,
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NICKEL: 5,
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PENNY: 1,
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};
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// console.log(currencyValue);
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// Now how much change is required?
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const changeRequired = adjustedCashGiven - adjustedPrice;
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// console.log(`Change Required ${changeRequired}`);
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// Two options, either set up the default object as
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// change["status"] = "INSUFFICIENT_FUNDS";
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// change["change"] = [];
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// which would remove two if checks below, OR leave it empty
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// and be explicit in the code
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let change = {};
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// Simplest case first.
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// If no change required
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if (changeRequired == 0) {
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change["status"] = "CLOSED";
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change["change"] = cid;
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// if the change required is more than the available cash in the drawer
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} else if (changeRequired > totalCashInDrawer) {
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change["status"] = "INSUFFICIENT_FUNDS";
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change["change"] = [];
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} else {
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let workingChange = changeRequired;
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let changeWithCash = {};
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availableCashInDrawer.forEach((denomination) => {
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// console.log(denomination);
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while (true) {
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const denominationName = denomination[0];
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const denominationValue = denomination[1];
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let currencyVal = currencyValues[denominationName];
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if (
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workingChange >= currencyValues[denominationName] &&
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denominationValue >= currencyVal
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) {
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denomination[1] -= currencyVal;
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workingChange -= currencyVal;
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let val = currencyVal / adjustmentAmount;
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if (changeWithCash[denominationName]) {
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changeWithCash[denominationName] += val;
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} else {
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changeWithCash[denominationName] = val;
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}
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} else {
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break;
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}
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}
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});
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// If we have calculated the change correctly, and there was exactly that
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// amount in the drawer, return closed and the cid (required for challenge)
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if (workingChange === 0 && changeRequired == totalCashInDrawer) {
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change["status"] = "CLOSED";
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change["change"] = cid;
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// otherwise if we have calculated change correctly, open the drawer and show what amount
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// to give.
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} else if (workingChange === 0) {
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change["status"] = "OPEN";
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change["change"] = Object.entries(changeWithCash);
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// Otherwise we have enough money in the cash drawer but not the right denominations to
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// give change, so return insufficent funds.
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} else {
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change["status"] = "INSUFFICIENT_FUNDS";
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change["change"] = [];
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}
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}
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console.log(change);
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return change;
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}
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checkCashRegister(19.5, 20, [
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["PENNY", 1.01],
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["NICKEL", 2.05],
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["DIME", 3.1],
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["QUARTER", 4.25],
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["ONE", 90],
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["FIVE", 55],
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["TEN", 20],
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["TWENTY", 60],
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["ONE HUNDRED", 100],
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]); // {status: "OPEN", change: [["QUARTER", 0.5]]}
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checkCashRegister(20, 20, [
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["PENNY", 1.01],
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["NICKEL", 2.05],
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["DIME", 3.1],
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["QUARTER", 4.25],
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["ONE", 90],
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["FIVE", 55],
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["TEN", 20],
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["TWENTY", 60],
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["ONE HUNDRED", 100],
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]); //{ status: 'CLOSED', change: [ [ 'PENNY', 1.01 ], [ 'NICKEL', 2.05 ], [ 'DIME', 3.1 ], [ 'QUARTER', 4.25 ], [ 'ONE', 90 ], [ 'FIVE', 55 ], [ 'TEN', 20 ], [ 'TWENTY', 60 ], [ 'ONE HUNDRED', 100 ] ] }
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checkCashRegister(19.5, 20, [
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["PENNY", 0.01],
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["NICKEL", 0],
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["DIME", 0],
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["QUARTER", 0],
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["ONE", 0],
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["FIVE", 0],
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["TEN", 0],
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["TWENTY", 0],
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["ONE HUNDRED", 0],
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]); // {status: "INSUFFICIENT_FUNDS", change: []}
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checkCashRegister(19.5, 20, [
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["PENNY", 0.5],
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["NICKEL", 0],
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["DIME", 0],
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["QUARTER", 0],
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["ONE", 0],
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["FIVE", 0],
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["TEN", 0],
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["TWENTY", 0],
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["ONE HUNDRED", 0],
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]);
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```
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