Codeforces Round #242 (Div. 2) C Magic Formulas

打个表，记录1到下标为止所有数的XOR值即可

 

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;
int array[1000001];
int main(){
    int cnt, i, j, k, t, n, num;
    int temp = 0;
    for(k = 0 ;k <= 1000000 ; k++){
        temp ^= k;
        array[k] = temp;
    }
    while(EOF != scanf("%d",&n)){
        cnt = 0;
        for(i = 1; i <= n; i++){
            scanf("%d",&num);
            cnt ^= num;
        }
        for(i = 1 ;i <= n; i++){
            int tmp_q = n / i;
            int tmp_w = n % i;
            while(tmp_q--){
                cnt ^= array[i-1];
            }
            if(tmp_w)
                cnt ^= array[tmp_w];
        }
        printf("%d\n",cnt);
    }
    return 0;
}