Submission #468402

#	Time	Username	Problem	Language	Result	Execution time	Memory
468402		cpp219	XOR Sum (info1cup17_xorsum)	C++14	7 / 100	1684 ms	25068 KiB

xorsum

#include <bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
#define debug(y) cout<<y,exit(0)
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 1e6 + 9;
const ll Log2 = 23;
const ll inf = 1e9 + 7;

vector<ll> g[2];
ll n,a[N],pos[N],val[N],ans,b[N];

ll Getval(ll x,ll i){
    return (((1 << i + 1) - 1) & x);
}

bool chk(ll x,ll i){
    return (x >> i) & 1;
}

void updateArr(){
    for (ll i = 1;i <= n;i++) b[pos[i]] = a[i];
    for (ll i = 1;i <= n;i++) a[i] = b[i];
}

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        freopen(task".out","w",stdout);
    }
    cin>>n;
    for (ll i = 1;i <= n;i++) cin>>a[i];
    for (ll bit = 0;bit < 30;bit++){
        g[0].clear(); g[1].clear();
        for (ll i = 1;i <= n;i++) g[chk(a[i],bit)].push_back(i);
        ll now = 1;
        for (auto i : g[0]) pos[i] = now++;
        for (auto i : g[1]) pos[i] = now++;
        updateArr();
        for (ll i = 1;i <= n;i++) val[i] = Getval(a[i],bit);
        ll tmp = 0;
        for (ll i = 1;i <= n;i++){
            ll st = lower_bound(val + i,val + n + 1,(1 << bit) - val[i]) - val;
            ll en = upper_bound(val + i,val + n + 1,(1 << bit + 1) - 1 - val[i]) - val - 1;
            tmp += en - st + 1;
            st = lower_bound(val + i,val + n + 1,(1 << bit) + (1 << bit + 1) - val[i]) - val;
            en = upper_bound(val + i,val + n + 1,(1 << bit + 2) - 2 - val[i]) - val - 1;
            tmp += en - st + 1; //debug(tmp);
            //cout<<tmp<<"\n";
        }
        tmp %= 2; //debug(tmp);
        ans += tmp*(1 << bit);
    }
    cout<<ans;
}

/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?)
	* do smth instead of nothing and stay organized
	* WRITE STUFF DOWN
	* DON'T GET STUCK ON ONE APPROACH
*/

Compilation message (stderr)

xorsum.cpp: In function 'int Getval(int, int)':
xorsum.cpp:17:22: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   17 |     return (((1 << i + 1) - 1) & x);
      |                    ~~^~~
xorsum.cpp: In function 'int main()':
xorsum.cpp:49:63: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   49 |             ll en = upper_bound(val + i,val + n + 1,(1 << bit + 1) - 1 - val[i]) - val - 1;
      |                                                           ~~~~^~~
xorsum.cpp:51:73: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   51 |             st = lower_bound(val + i,val + n + 1,(1 << bit) + (1 << bit + 1) - val[i]) - val;
      |                                                                     ~~~~^~~
xorsum.cpp:52:60: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   52 |             en = upper_bound(val + i,val + n + 1,(1 << bit + 2) - 2 - val[i]) - val - 1;
      |                                                        ~~~~^~~
xorsum.cpp:33:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
xorsum.cpp:34:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 38
• Subtask 5: 0 / 23