HDU - 5338 ZZX and Permutations 线段树 + set

感觉分情况讨论清楚就好啦， 不是很难写。

#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);

using namespace std;

const int N = 1e5 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 998244353;
const double eps = 1e-8;
const double PI = acos(-1);

template<class T, class S> inline void add(T& a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T& a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T& a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T& a, S b) {return a > b ? a = b, true : false;}

int n, a[N], pos[N], from[N], ans[N];
bool ban[N];
set<int> segEnd;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1

struct segmentTree {
    PII mx[N << 2];
    void build(int *a, int l, int r, int rt) {
        if(l == r) {
            mx[rt].fi = a[l];
            mx[rt].se = l;
            return;
        }
        int mid = l + r >> 1;
        build(a, lson); build(a, rson);
        mx[rt] = max(mx[rt << 1], mx[rt << 1 | 1]);
    }
    void update(int p, int l, int r, int rt) {
        if(l == r) {
            mx[rt].fi = 0;
            return;
        }
        int mid = l + r >> 1;
        if(p <= mid) update(p, lson);
        else update(p, rson);
        mx[rt] = max(mx[rt << 1], mx[rt << 1 | 1]);
    }
    PII query(int L, int R, int l, int r, int rt) {
        if(R < l || r < L || R < L) return mk(0, 0);
        if(L <= l && r <= R) return mx[rt];
        int mid = l + r >> 1;
        return max(query(L, R, lson), query(L, R, rson));
    }
} Tree;

int main() {
    int T; scanf("%d", &T);
    while(T--) {
        segEnd.clear();
        scanf("%d", &n);
        segEnd.insert(n + 1);
        segEnd.insert(0);
        for(int i = 1; i <= n; i++) {
            scanf("%d", &a[i]);
            pos[a[i]] = i;
            ban[i] = false;
            from[i] = i;
        }
        Tree.build(a, 1, n, 1);
        for(int i = 1; i <= n; i++) {
            int p = pos[i];
            if(ban[p]) continue;
            int R = from[p];
            PII tmp1 = mk(0, 0), tmp2 = mk(0, 0);
            auto it = segEnd.lower_bound(p);
            if(*it != p + 1) tmp1 = mk(a[p + 1], p + 1);
            --it;
            int L = *it + 1;
            tmp2 = Tree.query(L, R, 1, n, 1);
            if(tmp1 > tmp2) {
                ans[i] = tmp1.fi;
                from[tmp1.se] = from[p];
                Tree.update(tmp1.se, 1, n, 1);
            } else {
                ans[i] = tmp2.fi;
                L = tmp2.se, R = p;
                for(int j = L; j <= R; j++) {
                    Tree.update(j, 1, n, 1);
                    ban[j] = true;
                    if(j < R) ans[a[j]] = a[j + 1];
                }
                segEnd.insert(p);
                segEnd.insert(L);
            }
        }
        for(int i = 1; i <= n; i++) printf("%d%c", ans[i], " \n"[i == n]);
    }
    return 0;
}

/*
*/

标签：HDU,set,const,ZZX,int,segEnd,long,mod,define
来源： https://www.cnblogs.com/CJLHY/p/10927379.html