Java版快速排序[不稳定]

“`” 原理：分治+递归

复杂度：O(nlgn) – O(nlgn) – O(n^2) – O(1)[平均 – 最好 – 最坏 – 空间复杂度]

栈空间0(lgn) – O(n)

<pre><code class=""language-java"" lang=""java"">// 固定基准
public void quickSort(int[] a, int low, int high) {
if (null == a || a.length < 2) {
return;
}
if (low < high) {
int mid = partition(a, low, high);
quickSort(a, low, mid-1);
quickSort(a, mid+1, high);
}
}

private int partition(int[] a, int low, int high) {
int pivot = a[low];

while (low < high) {
// 注意等于，否则死循环
while (low < high && a[high] >= pivot) {
high–;
}
a[low] = a[high];
// 注意等于，否则死循环
while (low < high && a[low] <= pivot) {
low++;
}
a[high] = a[low];
}
a[low] = pivot;

return low;
}
</code></pre>

<pre><code> "“`