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import addStrings from "../add-strings/index.ts";
function multiply(x: string, y: string): string {    // console.log('mul', x, y);    if (x.length === 0 || y.length === 0) {        throw Error("invalid empty number");    }
    if (        Array.prototype.every.call(y, (s) => s === "0") ||        Array.prototype.every.call(x, (s) => s === "0")    ) {        return "0";    }
    if (x === "1") {        return y;    }
    if (y === "1") {        return x;    }
    if (y === "2") {        return addStrings(x, x);    }    if (x === "2") {        return addStrings(y, y);    }
    if (x.length + y.length < 16) {        return String(Number(x) * Number(y));    }    if (x.length > y.length) {        if (x.length >= 2) {            const half = Math.floor(x.length / 2);            return addStrings(                multiply(y, x.slice(0, half)) + "0".repeat(x.length - half),                multiply(y, x.slice(half)),            );        }    } else {        if (y.length >= 2) {            const half = Math.floor(y.length / 2);            return addStrings(                multiply(x, y.slice(0, half)) + "0".repeat(y.length - half),                multiply(x, y.slice(half)),            );        }    }
    throw Error("unreachable");}
export default multiply;// export default function multiply(x: string, y: string): string {//     // console.log('mul', x, y);//     if (x.length === 0 || y.length === 0) throw Error("invalid empty number");
//     if (//         Array.prototype.every.call(y, (s) => s === "0") ||//         Array.prototype.every.call(x, (s) => s === "0")//     ) {//         return "0";//     }
//     if (x === "1") return y;
//     if (y === "1") return x;
//     if (x.length < y.length) return multiply(y, x);
//     if (y === "2") return addStrings(x, x);//     if (y.length >= 2) {//         const half = Math.floor(y.length / 2);//         return addStrings(//             multiply(x, y.slice(0, half)) + "0".repeat(y.length - half),//             multiply(x, y.slice(half)),//         );//     }//     if (y === "4") return multiply("2", multiply(x, "2"));
//     if (y === "8") return multiply(multiply(x, "4"), "2");
//     if (["9", "7", "5", "3"].includes(y)) {//         return addStrings(x, multiply(x, String(Number(y) - 1)));//     }//     if (y === "6") return multiply(addStrings(x, x), String(Number(y) >> 1));//     throw new Error("unreachable");// }