Codeforces 193D Two Segments (线段树)

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <vector>#include <queue>#include <map>#include <set>#include <algorithm>#include <ctime>#include <cstdlib>#include <functional>#pragma comment(linker,"/STACK:102400000,102400000")using namespace std;#define eps 1e-10#define N 300030#define B 20#define M 3000020#define inf 0x3f3f3f3f#define LL long long#define pii pair<int, int>#define MP make_pair#define fi first#define se second#define mod 1000000007#define ls (i << 1)#define rs (ls | 1)#define md (ll + rr >> 1)#define lson ll, md, ls#define rson md + 1, rr, rsint mi1[N << 2], mi2[N << 2], s1[N << 2], s2[N << 2], lazy[N << 2];int n, a[N], f[N];void build(int ll, int rr, int i) {mi1[i] = 0, s1[i] = rr - ll + 1;mi2[i] = inf, s2[i] = 0;if(ll == rr) return;build(lson);build(rson);}LL ans;int t;void upd(int v, int i) {mi1[i] += v;mi2[i] += v;lazy[i] += v;}void push_down(int i) {if(lazy[i]) {upd(lazy[i], ls);upd(lazy[i], rs);lazy[i] = 0;}}void calc(int i, int x, int v) {if(v == 0) return;if(x < mi1[i]) {mi2[i] = mi1[i], s2[i] = s1[i];mi1[i] = x, s1[i] = v;}else if(x == mi1[i]) {s1[i] += v;}else if(x < mi2[i]) {mi2[i] = x, s2[i] = v;}else if(x == mi2[i]) {s2[i] += v;}}void push_up(int i) {mi1[i] = mi1[ls], s1[i] = s1[ls];mi2[i] = mi2[ls], s2[i] = s2[ls];calc(i, mi1[rs], s1[rs]);calc(i, mi2[rs], s2[rs]);}void update(int l, int r, int v, int ll, int rr, int i) {if(ll == l && rr == r) {upd(v, i);return;}push_down(i);if(r <= md) update(l, r, v, lson);else if(l > md) update(l, r, v, rson);else {update(l, md, v, lson);update(md + 1, r, v, rson);}push_up(i);}void query(int l, int r, int ll, int rr, int i) {if(ll == l && rr == r) {calc(t, mi1[i], s1[i]);calc(t, mi2[i], s2[i]);return;}push_down(i);if(r <= md) query(l, r, lson);else if(l > md) query(l, r, rson);else {query(l, md, lson);query(md + 1, r, rson);}}int main() {scanf("%d", &n);for(int i = 1; i <= n; ++i) {scanf("%d", &a[i]);f[a[i]] = i;}build(1, n, 1);ans = 0;t = (N << 2) - 1;for(int i = 1; i <= n; ++i) {int l = -1, r = -1;if(f[i] > 1 && a[f[i] - 1] <= i) l = a[f[i] - 1];if(f[i] < n && a[f[i] + 1] <= i) r = a[f[i] + 1];if(l > r) swap(l, r);if(r == -1) update(1, i, 1, 1, n, 1);else if(l == -1) {update(r + 1, i, 1, 1, n, 1);}else {update(r + 1, i, 1, 1, n, 1);update(1, l, -1, 1, n, 1);}mi1[t] = inf, mi2[t] = inf;query(1, i, 1, n, 1);if(mi1[t] == 1) ans += s1[t];if(mi2[t] == 2) ans += s2[t];}printf("%lld\n", ans - n);return 0;}