CF1731 C. Even Subarrays(思维+前缀异或和)

传送门

#include 

using namespace std;

#define endl "\n"
#define debug cout<<"debug"< PII;
const double eps = 1e-8;
const double PI = 3.14159265358979323;
const int N = 1e6+10, M = 2*N, mod = 1e9+7;
const int INF = 0x3f3f3f3f;

int n;

void solve()
{
    int n; cin>>n;
    vector a(n), cnt(2*n);
    for(int i = 0; i>a[i];
    ll res = 1ll*n*(n+1)/2;
    int pre = 0;
    cnt[0]++;
    // s[l~r] = s[r]^s[l-1]
    // s[i] = pre^=a[i], s[i]^(j*j) = s[x] --> s[i]^s[x] = j*j = s[x+1 ~ r], x为某个前缀x个的异或和
    // 记录所有前缀异或和的值, 再用当前的异或和 去找前缀异或和 即可遍历所有的区间的异或和
    for(int i = 0; i>T;
    while(T -- )
    {
        solve();
    }
    return 0;
}