//    a = a ^ b;

//    b = a ^ b;

//    a = a ^ b;

void swap(T& a, T& b) {

T t = a;

a = b;

b = t;

}

/*

* 快速排序

*/

void sort(T arr[], int len) {

if(len < 2) {
     return; }

swap(*arr, arr[len>>1]);

T* left = arr + 1;

T* right = arr + len + 1;

T bound = *arr;

while(left < right) {

while(*left < bound && left < right) left++;

while(*right >= bound && right > arr) right--;

if(left < right) {
     swap(*right, *left); }

}

if(bound > *right) {
     swap(*arr, *right); }

sort(arr, right-arr);

sort(right+1, len+arr-right-1);

}