js 全排列算法

var Perm = function ( arr ) {
	this.arr = arr;
}
Perm.prototype.list = function() {
	var arr = this.arr;
	var returnArray = [];
	var _swap = function ( indexA , indexB ) {
		if ( indexA == indexB ) return ;
		var tmp = arr[ indexB ];
		arr[ indexB ] = arr[ indexA ];
		arr[ indexA ] = tmp;
	} 
	var _perm = function ( k , m ) {
		if ( k == m ) {
			returnArray.push( arr.slice( 0 , m+1 ) );
		} else {
			for (var i = k; i <= m; i++) {
				_swap( k , i );
				_perm( k+1 , m );
				_swap( k , i );
			};
		}
	}
	_perm( 0 , arr.length - 1 );
	return returnArray;
};

//test
var arr = [1,2,3,4,5];
var perm = new Perm(arr);
var resultArr = perm.list();
for (var i = 0; i < resultArr.length; i++) {
	console.log( resultArr[i]);
};