代码

#include <string.h>
#include <algorithm>

#pragma GCC push_options
#pragma GCC optimize ("unroll-loops")

void LSD_Radix_Sort(unsigned *a, int n) {
	unsigned _b[n];
	unsigned *b = _b;
	
	int cnt[256];
	for (int i = 0; i < 32; i += 8) {
		memset(cnt, 0, sizeof(cnt));
		for (int j = 0; j < n; j++) cnt[(a[j] >> i) & 255]++;
		for (int j = 1; j < 256; j++) cnt[j] += cnt[j - 1];
		for (int j = n - 1; j >= 0; j--) b[--cnt[(a[j] >> i) & 255]] = a[j];
		std::swap(a, b);
	}
}

void sort(unsigned *a, int n) {
	LSD_Radix_Sort(a, n);
}

#pragma GCC pop_options

评测结果