uva12436 回头再做一次

线段树维护等差数列，结点维护首项+公差即可

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

typedef long long ll;
const int maxn = ;

#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)
int lc[maxn << ], rc[maxn << ], v[maxn << ];
ll nd[maxn << ], ad[maxn << ], s[maxn << ];

void pushup(int u);
void pushdown (int u);

inline int length(int u) {
    return rc[u] - lc[u] + ;
}

inline void change (int u, ll a) {
    v[u] = ;
    ad[u] = ;
    nd[u] = a;
    s[u] = a * length(u);
}

inline void maintain (int u, ll a, ll d) {
    if (v[u] && lc[u] != rc[u]) {
        pushdown(u);
        pushup(u);
    }

    v[u] = ;
    nd[u] += a;
    ad[u] += d;
    ll n = length(u);
    s[u] += a * n + (((n-) * n) / ) * d;
}

inline void pushup (int u) {
    s[u] = s[lson(u)] + s[rson(u)];
}

inline void pushdown (int u) {
    if (v[u]) {
        change(lson(u), nd[u]);
        change(rson(u), nd[u]);
        v[u] = nd[u] = ;
    } else if (nd[u] || ad[u]) {
        maintain(lson(u), nd[u], ad[u]);
        maintain(rson(u), nd[u] + length(lson(u)) * ad[u], ad[u]);
        nd[u] = ad[u] = ;
    }
}

void build (int u, int l, int r) {
    lc[u] = l;
    rc[u] = r;
    nd[u] = ad[u] = s[u] = ;

    if (l == r)
        return;
    int mid = (l + r) / ;
    build(lson(u), l, mid);
    build(rson(u), mid + , r);
    pushup(u);
}

void modify(int u, int l, int r, ll a, ll d) {
    if (l <= lc[u] && rc[u] <= r) {
        maintain(u, a + d * (lc[u] - l), d);
        return;
    }

    pushdown(u);
    int mid = (lc[u] + rc[u]) / ;
    if (l <= mid)
        modify(lson(u), l, r, a, d);
    if (r > mid)
        modify(rson(u), l, r, a, d);
    pushup(u);
}

void set(int u, int l, int r, ll a) {
    if (l <= lc[u] && rc[u] <= r) {
        change(u, a);
        return;
    }

    pushdown(u);
    int mid = (lc[u] + rc[u]) / ;
    if (l <= mid)
        set(lson(u), l, r, a);
    if (r > mid)
        set(rson(u), l, r, a);
    pushup(u);
}

ll query (int u, int l, int r) {
    if (l <= lc[u] && rc[u] <= r)
        return s[u];

    pushdown(u);
    ll ret = ;
    int mid = (lc[u] + rc[u]) / ;
    if (l <= mid)
        ret += query(lson(u), l, r);
    if (r > mid)
        ret += query(rson(u), l, r);
    pushdown(u);
    return ret;
}

int N;

int main () {
    while (~scanf("%d", &N)) {
        char op[];
        int l, r, x;
        build(, , );
        while (N--) {
            scanf("%s%d%d", op, &l, &r);
            if (op[] == 'A')
                modify(, l, r, , );
            else if (op[] == 'B')
                modify(, l, r, r - l + , -);
            else if (op[] == 'C') {
                scanf("%d", &x);
                set(, l, r, x);
            } else
                printf("%lld\n", query(, l, r));
        }
    }
    return ;
}