LeetCode刷题指南之排序篇--快速排序

//写法一
class Resulotion{
public:
	void quickSort(vector &arr, int left, int right){
		if (left >= right) return;
		int p = partition(arr, left, right);
		quickSort(arr, left, p - 1);
		quickSort(arr, p + 1, right);
	}
	int partition(vector &arr, int left, int right){

		int e = arr[left];
		//element: [left+1, j]v
		int j = left, i = left + 1;
		for (i; i <= right; i++){
			if (arr[i] < e)
				swap(arr[++j], arr[i]);
		}
		swap(arr[left], arr[j]);
		return j;
	}
};

//写法二
int partition(vector &arr, int left, int right){
int v = arr[left];

//[left+1,j] < v,  v < [j+1, i]
int j = left;
for (int i = left + 1; i <= right; i++){
if (arr[i] < v)
swap(arr[++j], arr[i]);
}
swap(arr[left], arr[j]);
return j;
}

void _quickSort(vector &arr, int left, int right){
if (left >= right) return;

int p = partition(arr, left, right);
_quickSort(arr, left, p - 1);
_quickSort(arr, p + 1, right);
}

void quickSort(vector &arr){
_quickSort(arr, 0, arr.size() - 1);
}