[zoj3632]线段树的应用

题意：f[i] = min(f[i+L]~f[i+R]) + x，计算f数组。从大到小计算即可，用线段树维护一下。

#pragma comment(linker, "/STACK:10240000,10240000")

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <map>
#include <queue>
#include <deque>
#include <cmath>
#include <vector>
#include <ctime>
#include <cctype>
#include <set>

using namespace std;

#define mem0(a) memset(a, 0, sizeof(a))
#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1
#define define_m int m = (l + r) >> 1
#define rep(a, b) for (int a = 0; a < b; a++)
#define rrep(a, b) for (int a = (b - 1); a >= 0; a--)
#define all(a) (a).begin(), (a).end()
#define lowbit(x) ((x) & (-(x)))
#define constructInt4(name, a, b, c, d) name(int a = 0, int b = 0, int c = 0, int d = 0): a(a), b(b), c(c), d(d) {}
#define constructInt3(name, a, b, c) name(int a = 0, int b = 0, int c = 0): a(a), b(b), c(c) {}
#define constructInt2(name, a, b) name(int a = 0, int b = 0): a(a), b(b) {}
#define pc(a) putchar(a)
#define ps(a) printf("%s", a)
#define pd(a) printf("%d", a)
#define sd(a) scanf("%d", &a)

typedef double db;
typedef long long LL;
typedef pair<int, int> pii;
typedef multiset<int> msi;
typedef set<int> si;
typedef vector<int> vi;
typedef map<int, int> mii;

const int dx[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int dy[8] = {1, 0, -1, 0, -1, 1, 1, -1};
const int maxn = 5 * 1e4 + 7;
const int maxm = 1e5 + 7;
const int minv = 1e7 + 7;
const int max_val = 1e6 + 7;
const int MD = 1e9 +7;
const LL INF = 1e15;
const double PI = acos(-1.0);
const double eps = 1e-10;

template<class T> T gcd(T a, T b) { return b == 0? a : gcd(b, a % b); }

struct SegTree {
    LL minv[maxn << 2];
    void build(int l, int r, int rt) {
        minv[rt] = INF;
        if (l == r) return ;
        define_m;
        build(lson);
        build(rson);
    }
    LL get(int L, int R, int l, int r, int rt) {
        if (L <= l && r <= R) return minv[rt];
        define_m;
        LL res = INF;
        if (L <= m) res = min(res, get(L, R, lson));
        if (R > m) res = min(res, get(L, R, rson));
        return res;
    }
    void update(int p, LL x, int l, int r, int rt) {
        if (l == r) {
            minv[rt] = x;
            return ;
        }
        define_m;
        if (p <= m) update(p, x, lson);
        else update(p, x, rson);
        minv[rt] = min(minv[rt << 1], minv[rt << 1 | 1]);
    }
};

SegTree st;
int cost[maxn], len[maxn];
int main() {
    //freopen("in.txt", "r", stdin);
    int n;
    while (cin >> n) {
        rep(i, n) sd(cost[i]);
        rep(i, n) sd(len[i]);
        st.build(1, n, 1);
        rrep(i, n) {
            LL x = cost[i];
            if (i + len[i] < n) x  += st.get(i + 1, i + 1 + len[i], 1, n, 1);
            st.update(i + 1, x, 1, n, 1);
        }
        cout << st.get(1, 1, 1, n, 1) << endl;
    }
    return 0;
}