Submission #1690744

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

const int N = 202020;

inline char get(void) {
	static char buf[100000], *S = buf, *T = buf;
	if (S == T) {
		T = (S = buf) + fread(buf, 1, 100000, stdin);
		if (S == T) return EOF;
	}
	return *S++;
}
template<typename T>
inline void read(T &x) {
	static char c; x = 0; int sgn = 0;
	for (c = get(); c < '0' || c > '9'; c = get()) if (c == '-') sgn = 1;
	for (; c >= '0' && c <= '9'; c = get()) x = x * 10 + c - '0';
	if (sgn) x = -x;
}

int a[N];
int n, l, r;
struct Seg {
	int c[N];
	int mn[N << 2];
	inline int MinPos(int a, int b) {
		return c[a] < c[b] ? a : b;
	}
	inline void Build(int o, int l, int r) {
		if (l == r) return (void)(mn[o] = l);
		int mid = (l + r) >> 1;
		Build(o << 1, l, mid);
		Build(o << 1 | 1, mid + 1, r);
		mn[o] = MinPos(mn[o << 1], mn[o << 1 | 1]);
	}
	inline void Init(int fl) {
		for (int i = 0; i <= n; i++) c[i] = N;
		for (int i = fl; i <= n; i += 2)
			c[i] = a[i];
		Build(1, 1, n);
	}
	inline int MinPos(int o, int l, int r, int L, int R) {
		if (l >= L && r <= R) return mn[o];
		int mid = (l + r) >> 1, res = 0;
		if (L <= mid) res = MinPos(res, MinPos(o << 1, l, mid, L, R));
		if (R > mid) res = MinPos(res, MinPos(o << 1 | 1, mid + 1, r, L, R));
		return res;
	}
};
Seg S[2];
struct cpp {
	int l, r, s, t, fl;
	cpp(void) {}
	cpp(int _l, int _r, int f) {
		l = _l; r = _r; fl = f;
		s = S[fl].MinPos(1, 1, n, l, r);
		t = S[fl ^ 1].MinPos(1, 1, n, s, r);
	}
	inline bool operator <(const cpp &x) const{
		return a[s] > a[x.s];
	}
};
cpp x;
priority_queue<cpp> Q;

int main(void) {
	read(n);
	for (int i = 1; i <= n; i++) read(a[i]);
	S[1].Init(1); S[0].Init(2);
	Q.push(cpp(1, n, 1));
	while (!Q.empty()) {
		x = Q.top(); Q.pop();
		printf("%d %d ", a[x.s], a[x.t]);
		if (x.l < x.s) Q.push(cpp(x.l, x.s - 1, x.fl));
		if (x.t < x.r) Q.push(cpp(x.t + 1, x.r, x.fl));
		if (x.s + 1 < x.t) Q.push(cpp(x.s + 1, x.t - 1, x.fl ^ 1));
	}
	return 0;
}

Submission Info

Judge Result