洛谷P3722 [AH2017/HNOI2017]影魔(线段树)

#include<bits/stdc++.h>
#define LL long long 
using namespace std;
const int MAXN = 1e6 + 10, INF = 1e9 + 10;
inline int read() {
    char c = getchar(); int x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int N, M, p1, p2, a[MAXN], L[MAXN], R[MAXN];
LL ans[MAXN];
int ll[MAXN], rr[MAXN];
LL sum[MAXN], f[MAXN];
#define ls k << 1
#define rs k << 1 | 1
void ps(int k, int v) {
    sum[k] += (rr[k] - ll[k] + 1) * v;
    f[k] += v;
}
void pushdown(int k) {
    if(!f[k]) return ;
    ps(ls, f[k]); ps(rs, f[k]);
    f[k] = 0;
}
void update(int k) {
    sum[k] = sum[ls] + sum[rs];
}
void Build(int k, int l, int r) {
    ll[k] = l; rr[k] = r;
    if(l == r) return ;
    int mid = l + r >> 1;
    Build(ls, l, mid); Build(rs, mid + 1, r);
}
void IntAdd(int k, int l, int r, int ql, int qr, int v) {
    if(ql > qr) return ;
    if(ql <= l && r <= qr) {ps(k, v); return ;}
    pushdown(k);
    int mid = l + r >> 1;
    if(ql <= mid) IntAdd(ls, l, mid, ql, qr, v);
    if(qr  > mid) IntAdd(rs, mid + 1, r, ql, qr, v);
    update(k);
}
LL IntQuery(int k, int l, int r, int ql, int qr) {
    if(ql > qr) return 0;
    if(ql <= l && r <= qr) return sum[k];
    pushdown(k);
    int mid = l + r >> 1;
    if(ql > mid) return IntQuery(rs, mid + 1, r, ql, qr);
    else if(qr <= mid) return IntQuery(ls, l, mid, ql, qr);
    else return IntQuery(ls, l, mid, ql, qr) + IntQuery(rs, mid + 1, r, ql, qr);
}
struct Query {
    int l, r, val, id;
    bool operator < (const Query &rhs) const {
        return id < rhs.id;
    }
};
vector<Query> q[MAXN];
void Pre() {
    a[0] = INF; a[N + 1] = INF;
    static int st[MAXN], top = 0;
    for(int i = 1; i <= N + 1; i++) {
        while(top && a[i] > a[st[top]]) R[st[top--]] = i;
        L[i] = st[top];
        st[++top] = i;
    }
    for(int i = 1; i <= N; i++) {
        q[R[i]].push_back({L[i], L[i], p1, -R[i]});
        q[L[i]].push_back({i + 1, R[i] - 1, p2, -L[i]});
        q[R[i]].push_back({L[i] + 1, i - 1, p2, -R[i]});
    }
}

int main() {
    N = read(); M = read(); p1 = read(); p2 = read();
    for(int i = 1; i <= N; i++) a[i] = read();
    Pre();
    Build(1, 0, N + 1);
    for(int i = 1; i <= M; i++) {
        int a = read(), b = read();
        ans[i] = (b - a) * p1;
        q[a - 1].push_back({a, b, -1, i});
        q[b].push_back({a, b, 1, i});
    }
    for(int i = 0; i <= N; i++) {
        sort(q[i].begin(), q[i].end()); 
        for(auto &x : q[i]) {
            if(x.id < 0) IntAdd(1, 0, N + 1, x.l, x.r, x.val);
            else ans[x.id] += 1ll * x.val * (IntQuery(1, 0, N + 1, x.l, x.r));
        }
    }
    for(int i = 1; i <= M; i++) cout << ans[i] << "\n";
    return 0;
}