代码

#include <algorithm>

unsigned int t[100005]; // 归并排序的常见实现中, 需要一个临时数组用于归并结果
void mergesort(unsigned int a[], int l, int r) {
    if (l >= r) return;
    int mid = (l + r) >> 1;
    mergesort(a, l, mid);
    mergesort(a, mid+1, r);
    int p = l, q = mid+1, s = l;
    while (s <= r) {
        if (p >= mid || (q <= r && a[p] > a[q])) {
            t[s++] = a[q++];
        } else t[s++] = a[p++];
    }
    for (int i = l; i <= r; ++i) a[i] = t[i];
}

void sort(unsigned *a, int n) {
    mergesort(a, 0, n-1);
}

评测结果