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Copy pathmultiply.ts
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82 lines (64 loc) · 2.29 KB
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import { parseNumber, removeLeadingZeros, removeTrailingZeros } from "./utils";
/**
* Multiplies two numbers represented as strings.
* @param left
* @param right
* @returns
*/
export function multiply(left: string, right: string): string {
let num1 = parseNumber(left);
let num2 = parseNumber(right);
// Calculate total decimal places
let totalDecimalPlaces =
num1.fractionalPart.length + num2.fractionalPart.length;
// Combine integer and fractional parts to convert to whole numbers
let wholeNum1 = num1.integerPart + num1.fractionalPart;
let wholeNum2 = num2.integerPart + num2.fractionalPart;
// Remove leading zeros
wholeNum1 = removeLeadingZeros(wholeNum1);
wholeNum2 = removeLeadingZeros(wholeNum2);
// If either number is 0, the result is 0
if (wholeNum1 === "0" || wholeNum2 === "0") {
return "0";
}
// Initialize array to store the result
let result = Array(wholeNum1.length + wholeNum2.length).fill(0);
// Perform multiplication (as if calculating by hand)
for (let i = wholeNum1.length - 1; i >= 0; i--) {
for (let j = wholeNum2.length - 1; j >= 0; j--) {
let mul = parseInt(wholeNum1[i]) * parseInt(wholeNum2[j]);
let p1 = i + j;
let p2 = i + j + 1;
let sum = mul + result[p2];
result[p2] = sum % 10;
result[p1] += Math.floor(sum / 10);
}
}
// Convert result array to string
let resultStr = result.join("");
// Remove leading zeros
resultStr = removeLeadingZeros(resultStr);
// Adjust decimal point position
if (totalDecimalPlaces > 0) {
// Add leading '0' if result string is shorter than total decimal places
if (resultStr.length <= totalDecimalPlaces) {
resultStr = resultStr.padStart(totalDecimalPlaces + 1, "0");
}
let integerPart = resultStr.slice(0, -totalDecimalPlaces);
let fractionalPart = resultStr.slice(-totalDecimalPlaces);
// Remove trailing zeros
fractionalPart = removeTrailingZeros(fractionalPart);
if (fractionalPart !== "0") {
resultStr = integerPart + "." + fractionalPart;
} else {
resultStr = integerPart;
}
}
// Determine the sign of the result
let resultSign = num1.sign * num2.sign;
if (resultSign === -1 && resultStr !== "0") {
resultStr = "-" + resultStr;
}
return resultStr;
}
export default multiply;