问题
当数据量较大时(数组长度1000000),快速排序递归算法栈溢出,且实际运行时间也比其他算法长,我猜测是由于大量的函数调用。有人能分析一下吗?如何改进?
递归
private void quick_sort_recursive(int head, int rear) {
if (head > rear) return;
int i = head;
int j = rear;
int tmp = array[head];
while (i != j) {
while (i < j && array[j] >= tmp) j--;
while (i < j && array[i] <= tmp) i++;
if (i < j) {
array[i] = array[i] + array[j];
array[j] = array[i] - array[j];
array[i] = array[i] - array[j];
}
}
array[head] = array[i];
array[i] = tmp;
quick_sort_recursive(head, i - 1);
quick_sort_recursive(i + 1, rear);
}
public void quickSortRecursive() {
quick_sort_recursive(0, len - 1);
}
非递归
private void quick_sort_not_recursive(int head, int rear) {
Stack<Integer> stack = new Stack<Integer>();
stack.push(head);
stack.push(rear);
int i, j;
while (!stack.empty()) {
rear = stack.pop();
head = stack.pop();
i = head;
j = rear;
int key = array[head];
while (i != j) {
while (i < j && array[j] >= key) j--;
while (i < j && array[i] <= key) i++;
if (i < j) {
array[i] = array[i] + array[j];
array[j] = array[i] - array[j];
array[i] = array[i] - array[j];
}
}
array[head] = array[i];
array[i] = key;
if (i - 1 > head) {
stack.push(head);
stack.push(i-1);
}
if (i + 1 < rear) {
stack.push(i+1);
stack.push(rear);
}
}
}
public void quickSortNotRecursive(){
quick_sort_not_recursive(0,len-1);
}