[LibreOJ 2249][NOI2014]购票
转载请注明出处:http://danihao123.is-programmer.com/
在紧张刺激的等待之后终于肝掉了这道题……
本题的DP方程长成这样(其中\(a\)指\(v\)的某个满足距离限制的祖先,\(d_v\)指\(v\)到根的路径长):
\[f_v = min(f_a + p_v(d_v - d_a) + q_v)\]
化简之后发现:
\[f_v = q_v + p_v d_v + min(f_a - p_v d_a)\]
利用\(min\)中那一块很容易发现是截距式……但是问题在于,我们的转移来源是树上的连续一段祖先,怎样维护他们的凸包?
答案很狂暴啊……用树链剖分套上向量集那题的线段树套凸包,然后完了……
(注意一点细节:本题因为数据范围过大,故可能存在两个向量叉乘爆long long,所以在求凸包时如果直接用叉积判断是否需要删点会炸掉,建议用斜率判断)
代码:
#include <cstdio> #include <cstring> #include <cstdlib> #include <cctype> #include <algorithm> #include <utility> #include <vector> #include <queue> #include <deque> #include <cmath> #include <set> #include <climits> using ll = long long; using T = ll; using R = long double; const R eps = 1e-8; int sign(R x) { if(fabsl(x) < eps) { return 0; } else { if(x > (R(0.00))) { return 1; } else { return -1; } } } struct Point { T x, y; Point(T qx = 0LL, T qy = 0LL) { x = qx; y = qy; } }; using Vector = Point; Vector operator +(const Vector &a, const Vector &b) { return Vector(a.x + b.x, a.y + b.y); } Vector operator -(const Point &a, const Point &b) { return Vector(a.x - b.x, a.y - b.y); } Vector operator *(const Vector &a, T lam) { return Vector(a.x * lam, a.y * lam); } Vector operator *(T lam, const Vector &a) { return Vector(a.x * lam, a.y * lam); } inline T dot(const Vector &a, const Vector &b) { return (a.x * b.x + a.y * b.y); } inline T times(const Vector &a, const Vector &b) { return (a.x * b.y - a.y * b.x); } inline bool cmp(const Point &a, const Point &b) { if(a.x == b.x) { return a.y < b.y; } else { return a.x < b.x; } } inline R slope(const Vector &a) { R dx = a.x, dy = a.y; return (dy / dx); } inline void andrew(Point *P, int L, std::vector<Point> &bot, std::vector<Point> &top) { std::sort(P + 1, P + 1 + L, cmp); for(int i = 1; i <= L; i ++) { if(i != 1 && (P[i].x == P[i - 1].x)) continue; while(bot.size() > 1 && sign(slope(P[i] - bot.back()) - slope(bot.back() - bot[bot.size() - 2])) <= 0) { bot.pop_back(); } bot.push_back(P[i]); } for(int i = L; i >= 1; i --) { if(i != L && (P[i].x == P[i + 1].x)) continue; while(top.size() > 1 && sign(slope(P[i] - top.back()) - slope(top.back() - top[top.size() - 2])) <= 0) { top.pop_back(); } top.push_back(P[i]); } std::reverse(top.begin(), top.end()); } const int maxn = 200005; const int maxno = maxn << 2; const int N = 200000; bool zen[maxno]; std::vector<Point> bot[maxno], top[maxno]; Point P[maxn]; inline void maintain(int o, int L, int R) { static Point tmp[maxn]; const int lc = o << 1, rc = o << 1 | 1; const bool used = zen[o]; zen[o] = (zen[lc] && zen[rc]); if(zen[o] != used) { std::copy(P + L, P + R + 1, tmp + 1); int len = R - L + 1; andrew(tmp, len, bot[o], top[o]); } } void modify(int o, int L, int R, const int &p, const Point &v) { if(L == R) { zen[o] = true; P[L] = v; bot[o].push_back(v); top[o].push_back(v); } else { const int M = (L + R) / 2; if(p <= M) { modify(o << 1, L, M, p, v); } else { modify(o << 1 | 1, M + 1, R, p, v); } maintain(o, L, R); } } inline T calc_ans(T k, const Point &v) { return v.y - k * v.x; } inline T search(const std::vector<Point> &vec, const T &k) { int l = 0, r = vec.size() - 1; while(r - l > 2) { int lm = (l * 2 + r) / 3, rm = (2 * r + l) / 3; if((calc_ans(k, vec[lm]) > calc_ans(k, vec[rm]))) { l = lm; } else { r = rm; } } T ans = LLONG_MAX; for(int i = l; i <= r; i ++) { ans = std::min(ans, calc_ans(k, vec[i])); } return ans; } T query(int o, int L, int R, const int &ql, const int &qr, const T &k) { if(ql <= L && R <= qr) { return search(bot[o], k); } else { int M = (L + R) / 2; T ans = LLONG_MAX; if(ql <= M) { ans = std::min(ans, query(o << 1, L, M, ql, qr, k)); } if(qr > M) { ans = std::min(ans, query(o << 1 | 1, M + 1, R, ql, qr, k)); } return ans; } } int first[maxn]; int next[maxn << 1], to[maxn << 1]; ll dist[maxn << 1]; void add_edge(int u, int v, ll d) { static int cnt = 0; cnt ++; next[cnt] = first[u]; first[u] = cnt; to[cnt] = v; dist[cnt] = d; } int fa[maxn], dep[maxn], hson[maxn]; ll d[maxn]; int siz[maxn]; int bs[maxn][18]; void dfs_1(int x, int f = -1, int depth = 1) { fa[x] = bs[x][0] = f; dep[x] = depth; siz[x] = 1; int max_siz = 0; for(int i = first[x]; i; i = next[i]) { int v = to[i]; if(v != f) { d[v] = d[x] + dist[i]; dfs_1(v, x, depth + 1); siz[x] += siz[v]; if(siz[v] > max_siz) { hson[x] = v; max_siz = siz[v]; } } } } int dfn[maxn], tid[maxn], up[maxn]; void dfs_2(int x, int a = 1, int f = 0) { static int cnt = 0; dfn[x] = ++ cnt; tid[cnt] = x; up[x] = a; if(hson[x]) { dfs_2(hson[x], a, x); } else { return; } for(int i = first[x]; i; i = next[i]) { int v = to[i]; if(v != f && v != hson[x]) { dfs_2(v, v, x); } } } int k_anc(int x, ll k) { int yx = x; for(int j = 17; j >= 0; j --) { int a = bs[x][j]; if(a != -1 && d[yx] - d[a] <= k) { x = a; } } #ifdef LOCAL printf("%d's %lld-th anc : %d\n", yx, k, x); #endif return x; } int n; ll get_up(int x, int anc, ll k) { ll ans = LLONG_MAX; while(up[x] != up[anc]) { ans = std::min(ans, query(1, 1, n, dfn[up[x]], dfn[x], k)); x = fa[up[x]]; } return std::min(ans, query(1, 1, n, dfn[anc], dfn[x], k)); } ll p[maxn], q[maxn], l[maxn]; ll f[maxn]; void dp(int x) { #ifdef LOCAL printf("processing %d...\n", x); printf("d : %lld\n", d[x]); #endif if(x != 1) { #ifdef LOCAL printf("b : %lld\n", get_up(fa[x], k_anc(x, l[x]), p[x])); #endif f[x] = get_up(fa[x], k_anc(x, l[x]), p[x]) + d[x] * p[x] + q[x]; } else { f[x] = 0; } #ifdef LOCAL printf("ans : %lld\n", f[x]); #endif modify(1, 1, n, dfn[x], Point(d[x], f[x])); for(int i = first[x]; i; i = next[i]) { int v = to[i]; dp(v); } } int main() { int t; scanf("%d%d", &n, &t); for(int i = 2; i <= n; i ++) { int father; T s; scanf("%d%lld%lld%lld%lld", &father, &s, &p[i], &q[i], &l[i]); add_edge(father, i, s); } memset(bs, -1, sizeof(bs)); dfs_1(1); dfs_2(1); for(int j = 1; (1 << j) < n; j ++) { for(int i = 1; i <= n; i ++) { int a = bs[i][j - 1]; if(a != -1) { bs[i][j] = bs[a][j - 1]; } } } dp(1); for(int i = 2; i <= n; i ++) { printf("%lld\n", f[i]); } return 0; }
Aug 10, 2022 03:06:59 PM
Have you taken any Life Insurance Corporation term or investment policy, need to pay premium for quarterly, half yearly or annually? LIC loan interest payment online Here we deliberate you about how to pay the premium at LIC Login with or without registration. Most of the policy holders till now using old way to pay life insurance premium in cash by visiting branch. LIC online payment gateway allows the customers to make real time payment secured solution for the insurance due premiums for all. Where the registered customers allows to pay LIC Loan Interest and due in online which taken against for the insurance policy.