Time Limit:2000MS Memory Limit:262144KB
64bit IO Format:%I64d & %I64u
Submit
Status Practice CodeForces 424C
Description
People in the Tomskaya region like magic formulas very much. You can see some of them below.
Imagine you are given a sequence of positive integer numbers
p1,
p2, ...,
pn. Lets write down some magic formulas:
Here, "mod" means the operation of taking the residue after dividing.
The expression 
means applying the bitwise
xor (excluding "OR") operation to integers
x and y. The given operation exists in all modern programming languages. For example, in languages C++ and Java it is represented by "^", in
Pascal — by "xor".
People in the Tomskaya region like magic formulas very much, but they don‘t like to calculate them! Therefore you are given the sequence
p, calculate the value of
Q.
Input
The first line of the input contains the only integer n (1?≤?n?≤?106). The next line contains
n integers: p1,?p2,?...,?pn
(0?≤?pi?≤?2·109).
Output
The only line of output should contain a single integer — the value of
Q.
Sample Input
Input
3 1 2 3
Output
3
题意：如题。
思路：纵向分析，先是p1^……^pn。。。不说了，贴个网址，我觉得说的肯定比我清楚。http://www.tuicool.com/articles/InYrm2M
AC代码：
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <stdlib.h>
using namespace std;
int p;
int a[1000006];
int main(){
int n;
scanf("%d",&n);
int ans=0;
for(int i=1;i<=n;i++){
scanf("%d",&p);
ans^=p;
}
for(int i=1;i<=n;i++){
a[i]=a[i-1]^i;
if(n%(2*i)!=0){
int x=n%(2*i);
if(x>=i){
ans^=a[i-1];
x-=i;
}
ans^=a[x];
}
}
printf("%d\n",ans);
return 0;
}
Codeforces 424 C Magic Formulas,布布扣,bubuko.com