/**
 * 插入演算法
 * 從第2個元素開始如果比上一個元素小，上面的元素位置都往後挪移位，該元素放在最前面
 * */
function insertSort(numArr) {
	for(let i=1; i<numArr.length; ++i){
		if(numArr[i] < numArr[i-1]){
			let temp = numArr[i];
			let j = i;
			while (j > 0 && numArr[j - 1] >= temp){
				numArr[j] = numArr[j-1]
				j--;
			}
			numArr[j] = temp;
		}
	}
}
/**
 * 快排
 * 以一個元素為基準分成比他大和小的兩個部分，將這個元素放中間，遞迴下去
 * */
function quickSort(array){
	function swap(array,i,j) {
		let temp = array[i];
		array[i] = array[j];
		array[j] = temp;
	}
	
	function segmentation(array,left,right) {
		let index = left;
		let temp = array[right];
		for(let i = left; i < right; ++i){
			if(array[i] < temp){
				swap(array,index,i);
				index++;
			}
		}
		swap(array,right,index);
		return index;
	}
	
	function sort(array,left,right) {
		if(left > right){
			return;
		}
		console.log('before:',array);
		let index = segmentation(array,left,right);
		console.log('after:',array);
		sort(array,left,index - 1);
		sort(array,index + 1, right);
	}
	sort(array, 0, array.length - 1);
	return array;
}
// let testArr = [1,2,6,7,8,9,4,3];
// console.log(mergeSort(testArr));

/**
 * 歸併
 * 將陣列一直查分下去，然後組合排序
 * */
function mergeSort(array) {
	function swap(array,i,j) {
		let temp = array[j];
		let k = j;
		while (k > i) {
			array[k] = array[k-1];
			k--;
		}
		array[i] = temp;
	}
	function split(array,startIndex,endIndex) {
		if(startIndex < endIndex){
			let midIndex = startIndex + Math.floor((endIndex - startIndex)/2);
			split(array,startIndex,midIndex);
			split(array,midIndex+1,endIndex);
			merge(array,startIndex,midIndex,endIndex);
		}
	}
	function merge(array,startIndex,midIndex,endIndex) {
		let i = startIndex;
		let j = midIndex + 1;
		let k = 0;
		let temp = [];
		while (i < midIndex + 1 && j < endIndex + 1){
			if(array[i] < array[j]){
				temp[k++] = array[i++];
			}
			else{
				temp[k++] = array[j++];
			}
		}
		while (i != midIndex + 1){
			temp[k++] = array[i++];
		}
		while (j != endIndex + 1){
			temp[k++] = array[j++];
		}
		temp.forEach((tmp,index)=>{
			array[startIndex+index] = tmp;
		});
	}
	split(array,0,array.length - 1);
	return array;
}