[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 = 32780;
const int oo = 999999999;

#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 << 2];
int Ask[N], n, Answer, D[N], before, after;

inline int read(){
    int x = 0, f = 1; char c = gc;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = gc;}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', 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 - 1; T[jd].Max = -1;
    if(l == r) return ;
    int mid = (l + r) >> 1;
    build_tree(l, mid, lson);
    build_tree(mid + 1, r, rson);    
}

void Poi_G(int l, int r, int jd, int x){
    if(l == r) {T[jd].w = 1; T[jd].Max = l; T[jd].Min = l; return ;}
    int mid = (l + r) >> 1;
    if(x <= mid) Poi_G(l, mid, lson, x);
    else Poi_G(mid + 1, 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) >> 1;
    if(x <= mid) Sec_Min(l, mid, lson, x, y);
    if(y > mid)  Sec_Min(mid + 1, 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) >> 1;
    if(x <= mid) Sec_Max(l, mid, lson, x, y);
    if(y > mid)  Sec_Max(mid + 1, r, rson, x, y);
}

int main()
{
    n = read();
    for(int i = 1; i <= n; i ++) {A[i].data = read(); A[i].id = i;}
    sort(A + 1, A + n + 1, cmp);//按照权值进行排序
    Ask[A[1].id] = 1; D[1] = A[1].data; int Id = 2;//第i次访问的那个点在线段树中的位置
    for(int i = 2; i <= n; i ++){
        if(A[i].data == A[i - 1].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(1, Id, 1);//建树
    Answer += D[Ask[1]];//第1次访问的点在线段树中的位置所对应的权值
    Poi_G(1, Id, 1, Ask[1]);
    for(int i = 2; i <= n; i ++){
        if(!Ask[i]) continue ;
        before = - oo, after = oo;
        Sec_Max(1, Id, 1, 1, Ask[i]);
        Sec_Min(1, Id, 1, Ask[i] + 1, 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(1, Id, 1, Ask[i]);
    }
    cout << Answer;
    return 0;
}