Project Euler 240

/**
 * Copyright uwi ( http://wonderfl.net/user/uwi )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/vYcR
 */

package {
    import flash.display.Sprite;
    import flash.text.TextField;
    import flash.utils.getTimer;
    // @see http://projecteuler.net/index.php?section=problems&id=240
    public class Euler240 extends Sprite {
        private var _tf : TextField;

        // 数字の高い方から個数を決定していって、最後に組み合わせを出して全部足す。
        public function Euler240() {
            _tf = new TextField();
            _tf.width = 465;
            _tf.height = 465;
            addChild(_tf);
            
            var s : int = getTimer();
            tr(solve(5,6,3,15)); 
//            tr(solve(20,12,10,70));
            var g : int = getTimer();
            tr((g - s) + " ms");
        }

        private var _mul : Number;

        private function solve(n : int, nSide : int, top : int, sum : int) : MPI
        {
            var i : int;
            var mul : Number = 1;
            for(i = 1;i <= n;i++){
                mul *= i;
            }
            _mul = mul;
            return dfs(nSide, n, top, sum);
        }
        
        private function dfs(n : int, left : int, top : int, sum : int) : MPI
        {
            var i : int;
            if(left == 0){
                return sum == 0 ? new MPI(_mul) : null;
            }
            if(n == 0){
                return null;
            }
            
            var om : Number = _mul;
            var ret : MPI = new MPI(0);
            for(i = 0;i <= left;i++){
                if(i >= 2)_mul /= i;
                ret.add_(dfs(n - 1, left - i, top, sum));
                if(top > 0){
                    top--;
                    sum -= n;
                    if(sum < 0)break;
                }
            }
            _mul = om;
            return ret;
        }

        private function tr(...o : Array) : void
        {
            _tf.appendText(o + "\n");
            _tf.scrollV = _tf.maxScrollV;
        }
    }
}

class MPI
{
    public var d : Vector.<uint>;
    
    public function MPI(v : * = 0)
    {
        if(v is Number){
            d = Vector.<uint>([]);
            for(var n : Number = v;n != 0;n = Math.floor(n / 10))d.push(n % 10);
            if(v == 0)d.push(0);
        }else if(v is String){
            d = Vector.<uint>([]);
            for(var i : int = v.length - 1;i >= 0;i--){
                d.push(uint(v.charAt(i)));
            }
        }else if(v is Array){
            d = Vector.<uint>(v);
        }else if(v is Vector.<uint>){
            d = v.concat();
        }else if(v is MPI){
            d = v.d.concat();
        }
        if(d)shave();
    }
    
    public static function add(a : MPI, b : MPI) : MPI
    {
        if(b == null)return a;
        
        var ret : MPI = new MPI(a);
        var i : uint;
        var minl : uint = Math.min(ret.d.length, b.d.length);
        for(i = 0;i < minl;i++){
            ret.d[i] += b.d[i];
        }
        for(i = ret.d.length;i < b.d.length;i++){
            ret.d.push(b.d[i]);
        }
        ret.carry();
        return ret;
    }
    
    public function add_(b : MPI) : MPI
    {
        if(b == null)return this;
        
        var i : uint;
        var minl : uint = Math.min(this.d.length, b.d.length);
        for(i = 0;i < minl;i++){
            this.d[i] += b.d[i];
        }
        for(i = this.d.length;i < b.d.length;i++){
            this.d.push(b.d[i]);
        }
        this.carry();
        return this;
    }
    
    public static function addint(a : MPI, b : int) : MPI
    {
        var ret : MPI = new MPI(a);
        ret.d[0] += b;
        ret.carry();
        return ret;
    }
    
    public function addint_(b : int) : MPI
    {
        this.d[0] += b;
        this.carry();
        return this;
    }
    
    public function inc() : void
    {
        d[0]++;
        for(var i : uint = 0;i < d.length;i++){
            if(d[i] >= 10){
                var c : uint = d[i] / 10;
                if(i == d.length - 1){
                    d.push(0);
                }
                d[i + 1] += c;
                d[i] %= 10;
            }else{
                break;
            }
        }
    }
    
    public static function sub(a: MPI, b : MPI) : MPI
    {
        if(b == null)return a;
        if(comp(a, b) < 0){
            var m : MPI = a; a = b; b = m;
        }
        
        // a - b
        var ret : MPI = new MPI(a);
        var i : uint;
        for(i = 0;i < b.d.length;i++){
            ret.d[i] -= b.d[i];
        }
        
        ret.minuscarry();
        return ret;
    }
    
    public function sub_(b : MPI) : MPI
    {
        if(b == null)return this;
        
        // a - b
        var i : uint;
        for(i = 0;i < b.d.length;i++){
            this.d[i] -= b.d[i];
        }
        
        this.minuscarry();
        return this;
    }
    
    public static function subint(a : MPI, b : int) : MPI
    {
        var ret : MPI = new MPI(a);
        ret.d[0] -= b;
        ret.minuscarry();
        return ret;
    }
    
    public function subint_(b : int) : MPI
    {
        this.d[0] -= b;
        this.minuscarry();
        return this;
    }
    
    public static function comp(a : MPI, b : MPI) : int
    {
        if(a.d.length != b.d.length)return a.d.length - b.d.length;
        for(var i : uint = a.d.length - 1;i >= 0;i--){
            if(a.d[i] != b.d[i]){
                return a.d[i] - b.d[i];
            }
        }
        return 0;
    }
    
    public static function mul(a : MPI, b : MPI) : MPI
    {
        var retv : Vector.<uint> = new Vector.<uint>(a.d.length + b.d.length);
        var i : uint, j : uint;
        for(i = 0;i < retv.length;i++)retv[i] = 0;
        for(i = 0;i < a.d.length;i++){
            for(j = 0;j < b.d.length;j++){
                retv[i + j] += a.d[i] * b.d[j];
            }
        }
        var ret : MPI = new MPI(retv);
        ret.carry();
        ret.shave();
        return ret;
    }
    
    public static function mulint(a : MPI, b : int) : MPI
    {
        var ret : MPI = new MPI(a);
        for(var i : uint = 0;i < ret.d.length;i++){
            ret.d[i] *= b;
        }
        ret.carry();
        return ret;
    }
    
    public function mulint_(b : int) : MPI
    {
        for(var i : uint = 0;i < d.length;i++){
            this.d[i] *= b;
        }
        this.carry();
        return this;
    }
    
    public static function div(a : MPI, b : MPI) : Array
    {
        var bm : Array = new Array(10);
        var i : uint, j : uint;
        for(i = 1;i <= 9;i++)bm[i] = mulint(b, i);
        
        var retr : Vector.<uint> = Vector.<uint>([]);
        var m : MPI = new MPI(0);
        for(i = a.d.length - 1;i >= 0;i--){
            m.mul10(1);
            m = addint(m, a.d[i]);
            for(j = 1;j <= 9;j++){
                if(comp(m, bm[j]) < 0)break;
            }
            retr.push(j - 1);
            if(j >= 2)m.sub_(bm[j - 1]);
        }
        
        var ret : MPI = new MPI(retr.reverse());
        ret.shave();
        m.shave();
        return [ret, m];
    }
    
    public static function divint(a : MPI, b : int) : Array
    {
        var i : uint;
        
        var retr : Vector.<uint> = Vector.<uint>([]);
        var m : int = 0;
        for(i = a.d.length - 1;i >= 0;i--){
            m = m * 10 + a.d[i];
            var dv : int = m / b;
            retr.push(dv);
            m %= b;
        }
        
        var ret : MPI = new MPI(retr.reverse());
        ret.shave();
        return [ret, m];
    }
    
    // 末尾の0の個数
    public function nLast0() : int
    {
        for(var i : uint = 0;i < d.length && d[i] == 0;i++);
        return i;
    }
    
    // 位上げ
    public function carry() : void
    {
        for(var i : uint = 0;i < d.length;i++){
            if(d[i] >= 10){
                var c : uint = d[i] / 10;
                if(i == d.length - 1){
                    d.push(0);
                }
                d[i + 1] += c;
                d[i] %= 10;
            }
        }
    }
    
    // 位下げ
    public function minuscarry() : void
    {
        for(var i : uint = 0;i < d.length;i++){
            if(d[i] <= 2147483648)continue; // やっつけ
            var v : int = d[i] - 4294967296;
            var c : int = (-v + 9) / 10;
            d[i + 1] -= c;
            d[i] += 10 * c;
        }
        shave();
    }
    
    // 上位の桁から0を削る
    public function shave() : void
    {
        for(var i : uint = d.length - 1;i >= 1;i--){
            if(d[i] > 0)break;
            d.pop();
        }
    }
    
    public function mul10(x : int) : void
    {
        var r : Vector.<uint> = d.reverse();
        for(var i : uint = 0;i < x;i++){
            r.push(0);
        }
        d = r.reverse();
    }
    
    public function toString() : String
    {
        return d.concat().reverse().join('');
    } 
}