剑指offer-基础练习-快速排序-排序

Posted 2020-11-29 buaazhhx

/*
题目：快速排序
*/
/*
思路：将一个数组分为两份，左边的数字小于index，右边的数字大于index，递归划分后形成一个排序后的数组。
*/
void QuickSort(int data[],int length,int start,int end){
	if(start == end) return;
	int index = Partition(data,length,start,end);
	if(index > start){
		QuickSort(data,length,start,index-1);
	}
	if(index < end){
		QuickSort(data,length,index+1,end);
	}
}

int Partition(int data[],int length,int start,int end){
	if(data == null || length < 0 || start < 0 || end >= length){
		throw new std::exception("invalid Parameters");
	}
	
	int index = RandomInRange(start,end);
	Swap(&data[index],&data[end]);
	
	int small = start-1;
	for(int index = start; index < end; index++){
		if(data[index] < data[end]){
			small++;
			if(small != index){
				Swap(&data[small],&data[index]);
			}
		}
	}
	
	small++;
	Swap(&data[small],&data[end]);
	return small;
}