[HNOI2002]营业额统计 II

https://www.luogu.org/problemnew/show/2234

将权值离散化，以权值为下标建立权值线段树

#include <bits/stdc++.h>

using namespace std;
const int N = ;
const int oo = ;

#define gc getchar()
#define lson jd << 1
#define rson jd << 1 | 1

struct Node_1 {int data, id;} A[N];
struct Node_2 {int l, r, w, Max, Min;} T[N << ];
int Ask[N], n, Answer, D[N], before, after;

inline int read(){
    int x = , f = ; char c = gc;
    while(c < '' || c > '') {if(c == '-') f = -; c = gc;}
    while(c >= '' && c <= '') x = x *  + c - '', c = gc;
    return x * f;
}

bool cmp(Node_1 a, Node_1 b) {return a.data < b.data;}

void pushup(int jd){
    T[jd].w = T[lson].w + T[rson].w;
    T[jd].Max = max(T[lson].Max, T[rson].Max);
    T[jd].Min = min(T[lson].Min, T[rson].Min);
}

void build_tree(int l, int r, int jd){
    T[jd].l = l; T[jd].r = r; T[jd].Min = oo - ; T[jd].Max = -;
    if(l == r) return ;
    int mid = (l + r) >> ;
    build_tree(l, mid, lson);
    build_tree(mid + , r, rson);
}

void Poi_G(int l, int r, int jd, int x){
    if(l == r) {T[jd].w = ; T[jd].Max = l; T[jd].Min = l; return ;}
    int mid = (l + r) >> ;
    if(x <= mid) Poi_G(l, mid, lson, x);
    else Poi_G(mid + , r, rson, x);
    pushup(jd);
}

void Sec_Min(int l, int r, int jd, int x, int y){
    if(!T[jd].w) return ;
    if(x <= l && r <= y) {after = min(after, T[jd].Min); return ;}
    int mid = (l + r) >> ;
    if(x <= mid) Sec_Min(l, mid, lson, x, y);
    if(y > mid)  Sec_Min(mid + , r, rson, x, y);
}

void Sec_Max(int l, int r, int jd, int x, int y){
    if(!T[jd].w) return ;
    if(x <= l && r <= y)
    {before = max(before, T[jd].Max); return ;}
    int mid = (l + r) >> ;
    if(x <= mid) Sec_Max(l, mid, lson, x, y);
    if(y > mid)  Sec_Max(mid + , r, rson, x, y);
}

int main()
{
    n = read();
    for(int i = ; i <= n; i ++) {A[i].data = read(); A[i].id = i;}
    sort(A + , A + n + , cmp);//按照权值进行排序
    Ask[A[].id] = ; D[] = A[].data; int Id = ;//第i次访问的那个点在线段树中的位置
    for(int i = ; i <= n; i ++){
        if(A[i].data == A[i - ].data) continue ;
        Ask[A[i].id] = Id; D[Id] = A[i].data;//线段树中位置对应的点的权值
        Id ++;
    }
    Id --;
    build_tree(, Id, );//建树
    Answer += D[Ask[]];//第1次访问的点在线段树中的位置所对应的权值
    Poi_G(, Id, , Ask[]);
    for(int i = ; i <= n; i ++){
        if(!Ask[i]) continue ;
        before = - oo, after = oo;
        Sec_Max(, Id, , , Ask[i]);
        Sec_Min(, Id, , Ask[i] + , Id);
        if(before == - oo) Answer += D[after] - D[Ask[i]];
        else if(after == oo) Answer += D[Ask[i]] - D[before];
        else Answer += min(abs(D[Ask[i]] - D[before]), abs(D[Ask[i]] - D[after]));
        Poi_G(, Id, , Ask[i]);
    }
    cout << Answer;
    return ;
}