代码

#include <stdio.h>

int main() {
    static int n = 1 << 20;
    static int rev[1 << 20 | 5];
    for (int i = 0, j = 0; i < n; i ++) {
        rev[i] = j;
        for (int k = n >> 1; (j ^= k) < k; k >>= 1);
    }
    for (int i = 0; i < n; i ++) {
        ans += rev[i];
    }
    printf("%d\n", ans);
}

评测结果