Convert number to aheui expression

number2aheui.js

/**
 * TODO
 *    optimize algorithm
 *    support negative numbers
 */

var readline = require("readline");
var rl = readline.createInterface({input: process.stdin, output: process.stdout, terminal: false});

var cho = {"+": 3, "*": 4, "-": 16, "/": 2, ">": 8};
var jong = [0, 0, 1, 7, 16, 8, 18, 9, 15, 10];

function han_assemble(cho, jung, jong) {
    return String.fromCharCode(0xac00 + (((cho * 21) + jung) * 28) + jong);
}

function try_dis(num) {
    for(var i=2 ; i<=9 ; i++) {
        var nr = Math.floor(num / i);
        var diff = nr * i - num;

        if(Math.abs(diff) >= 2 && Math.abs(diff) <= 9)
            return get_expr(nr).concat([i, "*", Math.abs(diff), diff > 0 ? "-" : "+"]);

        else if(i * nr === num)
            return get_expr(nr).concat([i, "*"]);
    }
}

function try_sqrt(num) {
    var rt = Math.floor(Math.sqrt(num));
    var remainder = num - rt * rt;
    var exp_plus = get_expr(rt).concat(">", "*", get_expr(remainder), "+");

    rt = Math.ceil(Math.sqrt(num));
    remainder = rt * rt - num;
    var exp_minus = get_expr(rt).concat(">", "*", get_expr(remainder), "-");

    return exp_plus.length < exp_minus.length ? exp_plus : exp_minus;
}

function get_basic(num) {
    if(num === 0)
        return [2, 2, "-"];

    else if(num === 1)
        return [2, 2, "/"];

    else if(num >= 2 && num <= 9)
        return [num];

    else if(num >= 10 && num <= 18) {
        var n1 = Math.ceil(num / 2);
        var n2 = num - n1;
        return [n1, n2, "+"];
    }
}

function get_expr(num) {
    if(num <= 18) return get_basic(num);

    for(var i=2 ; i<=9 ; i++) {
        var nr = Math.floor(num / i);

        if(nr >= 2 && nr <= 9 && nr * i === num)
            return [i, nr, "*"];
    }

    var rt = Math.sqrt(num);
    if(Math.floor(rt) === rt)
        return get_expr(rt).concat([">", "*"]);

    var arr_dis = try_dis(num);
    var arr_sqrt = try_sqrt(num);

    return arr_dis.length < arr_sqrt.length ? arr_dis : arr_sqrt;
}

function get_aheui_expression(num) {
    if(num < 0) {
        console.log("not supported");
        return [];
    }

    if(num <= 18) return get_basic(num);

    var exp = get_expr(num);
    for(var i=2 ; i<=9 ; i++) {
        var temp = get_expr(num - i).concat([i, "+"]);
        if(temp.length < exp.length) exp = temp.slice(0);

        temp = get_expr(num + i).concat([i, "-"]);
        if(temp.length < exp.length) exp = temp.slice(0);
    }

    return exp;
}

rl.on("line", function(input) {
    var num = parseInt(input, 10);

    var expr =  get_aheui_expression(num);
    var expr_str = expr.join(" ");
    var output = "";

    for(var i in expr) {
        var v = expr[i];
        if(typeof v === "number") output += han_assemble(7, 0, jong[v]);
        else output += han_assemble(cho[v], 0, 0);
    }

    console.log(num + " = " + expr_str);
    console.log(output);
});