「CF424C」Magic Formulas
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:
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.
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).
The only line of output should contain a single integer — the value of Q.
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题解
首先通过交换律可得出变为ans=p1^p2^p3^…pn
然后ans^1-n这一段分别^1-n
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#include<iostream> #include<cstdio> #include<cstring> #define inf 0x7fffffff using namespace std; int n,ans; int x,f[1000001]; int main() { scanf("%d",&n); for(int i=1;i<=n;i++) { scanf("%d",&x); ans^=x; } for(int i=1;i<=n;i++)f[i]=f[i-1]^i; for(int i=1;i<=n;i++) { int t=n; t%=(2*i); if(t==i)ans^=f[i-1]; else if(t>i){ans^=f[i-1]^f[t-i];} else ans^=f[t]; } printf("%d",ans); return 0; } |
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