This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define m_p make_pair
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define fi first
#define se second
typedef long long ll;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
mt19937 rnf(2106);
const int N = 1003, m = 20;
int n, ty;
int a[N];
vector<pair<int, int> > ans;
void ubd(int x, int y)
{
ans.push_back(m_p(x, y));
a[x] ^= a[y];
}
void solv2()
{
int nn = n;
for (int j = m - 1; j >= 0; --j)
{
for (int i = 1; i < nn; ++i)
{
if ((a[i] & (1 << j)))
{
if ((a[i + 1] & (1 << j)))
ubd(i, i + 1);
else
{
ubd(i + 1, i);
ubd(i, i + 1);
}
}
}
if ((a[nn] & (1 << j)))
--nn;
}
for (int i = 1; i < n; ++i)
assert(a[i] <= a[i + 1]);
}
void solv1()
{
vector<int> v;
for (int i = 1; i <= n; ++i)
v.push_back(a[i]);
sort(all(v));
reverse(all(v));
for (int i = 0; i < sz(v); ++i)
{
int u = -1;
for (int j = 1; j <= n - i; ++j)
{
if (i)
{
if (a[j] == (v[i] ^ v[i - 1]))
u = j;
}
else
{
if (a[j] == v[i])
u = j;
}
}
for (int j = 1; j < n - i; ++j)
{
ubd(j, j + 1);
}
for (int j = u + 1; j <= n - i; ++j)
{
ubd(j, j - 1);
}
for (int j = u - 2; j >= 1; --j)
{
ubd(j, j + 1);
}
}
for (int i = n - 1; i >= 1; --i)
ubd(i, i + 1);
for (int i = 1; i < n; ++i)
assert(a[i] < a[i + 1]);
}
void solv()
{
cin >> n >> ty;
for (int i = 1; i <= n; ++i)
cin >> a[i];
if (ty == 2)
{
solv2();
}
else
{
solv1();
}
cout << sz(ans) << "\n";
for (int i = 0; i < sz(ans); ++i)
cout << ans[i].fi << ' ' << ans[i].se << "\n";
}
int main()
{
#ifdef SOMETHING
freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
#endif // SOMETHING
ios_base::sync_with_stdio(false), cin.tie(0);
int tt = 1;
//cin >> tt;
while (tt--)
{
solv();
}
return 0;
}
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