javascript实现合并排序

var merge = function(ary, p, q, r) {
	// eg. ary = [4, 1], p = 0, q = 0, r = 1
	var l_ary = ary.slice(p, q + 1);
	var r_ary = ary.slice(q + 1, r + 1);
	var b_ary;

	while (l_ary.length && r_ary.length) {
		ary[p++] = l_ary[0] <= r_ary[0] ? l_ary.shift() : r_ary.shift();	
	}

	b_ary = l_ary.length ? l_ary : r_ary;
	while (b_ary.length) {
		ary[p++] = b_ary.shift();
	}

	console.log(ary);
}

var merge_sort = function(ary, s, e) {
	var m;
	if (s === e) return;
	m = Math.floor((s + e) / 2);

	merge_sort(ary, s, m);
	merge_sort(ary, m + 1, e);
	merge(ary, s, m, e);
}

var do_merge_sort = function() {
	var ary = [4, 3, 7, 1, 9, 2, 6, 5];

	console.log(ary);
	merge_sort(ary, 0, ary.length - 1);

	console.log(ary);
} 

do_merge_sort();