具体原理可看这里
javascript版本：
function merge(left, right){
var result = [];
while (left.length > 0 && right.length > 0){
if (left[0] < right[0]){
result.push(left.shift());//把最小的最先取出，放到结果集中
} else {
result.push(right.shift());
}
} return result.concat(left).concat(right);//剩下的就是合并，这样就排好序了
}
function mergeSort(array){
if (array.length == 1) {
return array;
}
var middle = Math.floor(array.length / 2),//求出中点
left = array.slice(0, middle),//分割数组
right = array.slice(middle);
return merge(mergeSort(left), mergeSort(right));//递归合并与排序
}
ruby版本：
def merge(left, right)
final = []
until left.empty? or right.empty?
final << ( left.first < right.first ? left.shift : right.shift )
end
final + left + right
end
def mergeSort(array)
return array if array.size < 2
left = array.first(array.size/2)
right = array.last(array.size - array.size/2)
merge(mergeSort(left), mergeSort(right))
end