Submission #9813519

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Source Code Expand

#include <bits/stdc++.h>

#define reg register
#define pr std::pair<ll, int>
#define fi first
#define se second
#define FIN(s) freopen(s, "r", stdin)
#define FOUT(s) freopen(s, "w", stdout)
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define rep(i, l, r) for (int i = l; i <= r; ++i)
#define lep(i, l, r) for (int i = l; i < r; ++i)
#define irep(i, r, l) for (int i = r; i >= l; --i)
#define ilep(i, r, l) for (int i = r; i > l; --i)
#define Rep(i, n) rep(i, 1, n)
#define Lep(i, n) lep(i, 1, n)
#define IRep(i, n) irep(i, n, 1)
#define ILep(i, n) ilep(i, n, 1)
typedef long long ll;
typedef long double ld;

namespace modular {
    const int MOD = 1000000007;
    inline int add(int x, int y) { return (x += y) >= MOD ? x -= MOD : x; }
    inline void inc(int &x, int y) { (x += y) >= MOD ? x -= MOD : 0; }
    inline int mul(int x, int y) { return 1LL * x * y % MOD; }
    inline int qpow(int x, int y) {
        int ans = 1;
        for (; y; y >>= 1, x = mul(x, x))
            if (y & 1)
                ans = mul(ans, x);
        return ans;
    }
}; // namespace modular

namespace Base {
    template <typename Tp> inline Tp input() {
        Tp x = 0, y = 1;
        char c = getchar();
        while ((c < '0' || '9' < c) && c != EOF) {
            if (c == '-')
                y = -1;
            c = getchar();
        }
        if (c == EOF)
            return 0;
        while ('0' <= c && c <= '9')
            x = x * 10 + c - '0', c = getchar();
        return x *= y;
    }
    template <typename Tp> inline void read(Tp &x) { x = input<Tp>(); }
    template <typename Tp> inline void chmax(Tp &x, Tp y) { x < y ? x = y : 0; }
    template <typename Tp> inline void chmin(Tp &x, Tp y) { x > y ? x = y : 0; }
}; // namespace Base
using namespace Base;
/*----------------------------------------------------------------------------*/

#define MAX_N 200007
#define V std::vector

int N;
int sz[MAX_N];
ll d[MAX_N];
pr a[MAX_N];
V<int> G[MAX_N];
std::map<ll, int> mp;

void dfs1(int x, int las) {
    sz[x] = 1;
    for (int y : G[x])
        if (y != las) {
            dfs1(y, x);
            sz[x] += sz[y];
            d[x] += d[y] + sz[y];
        }
}

bool dfs2(int x, int las) {
    if (mp[d[x]] != x)
        return false;
    for (int y : G[x])
        if (y != las) {
            d[y] = d[x] + N - 2 * sz[y];
            if (!dfs2(y, x))
                return false;
        }
    return true;
}

void solve() {
    std::sort(a + 1, a + N + 1);
    Rep(i, N) sz[i] = 1, mp[a[i].fi] = a[i].se;
    ILep(i, N) {
        int u = a[i].se, s = N - 2 * sz[u], v;
        if (mp.count(a[i].fi - s)) {
            v = mp[a[i].fi - s];
            sz[v] += sz[u];
            G[u].push_back(v);
            G[v].push_back(u);
        } else
            return puts("-1"), void();
    }
    dfs1(1, 0);
    if (!dfs2(1, 0))
        return puts("-1"), void();
    Rep(i, N) {
        for (int j : G[i])
            if (i < j)
                printf("%d %d\n", i, j);
    }
}

int main() {
#ifdef LOCAL
    FIN("in");
#endif
    read(N);
    Rep(i, N) read(a[i].fi), a[i].se = i;
    solve();
    return 0;
}

Submission Info

Judge Result