代码

#include <stdio.h>
#define SIZE (200 << (20 - 2))

int A[SIZE];

unsigned _b[50000005];

void sort(unsigned *a, int n){
    const int S = 8;
    unsigned *b;
    unsigned cnt[256];
    int i;
    b = _b;
    for (i = 0; i < 32; i += S) {
        for (int j = 0; j < 256; j++) cnt[j] = 0;
        if (i + S >= 32) {
            for (int j = 0; j < n; j++) ++cnt[a[j] >> i];
            for (int j = 1; j < 1 << S; j++) cnt[j] += cnt[j - 1];
            for (int j = n - 1; j >= 0; j--) b[--cnt[a[j] >> i]] = a[j];
            unsigned *tmp = a;
            a = b, b = tmp;
            continue;
        }
        int t = (1 << S) - 1;
        for (int j = 0; j < n; j++) ++cnt[(a[j] >> i) & t];
        for (int j = 1; j < 1 << S; j++) cnt[j] += cnt[j - 1];
        for (int j = n - 1; j >= 0; j--) b[--cnt[(a[j] >> i) & t]] = a[j];
        unsigned *tmp = a;
        a = b, b = tmp;
    }
}

int main() {
	for (int i = 0; i < SIZE; i++) {
		A[i] = i ^ (i >> 5);
	}
	sort((unsigned *) A, 50000000);
	printf("%d\n", A[0]);
}

评测结果