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  • ZR#317.【18 提高 2】A(计算几何 二分)

    题意

    Sol

    非常好的一道题,幸亏这场比赛我没打,不然我估计要死在这个题上qwq

    到不是说有多难,关键是细节太多了,我和wcz口胡了一下我的思路,然后他写了一晚上没调出来qwq

    解法挺套路的,先提出一个$x$

    然后维护一堆直线对应的上凸壳

    在凸壳上二分即可。

    由于这题的$x$很小,直接处理出答案就行了

    /*
    
    */
    #include<iostream>
    #include<cstdio>
    #include<cstring>
    #include<algorithm>
    #include<map>
    #include<vector>
    #include<set>
    #include<queue>
    #include<cmath>
    //#include<ext/pb_ds/assoc_container.hpp>
    //#include<ext/pb_ds/hash_policy.hpp>
    #define Pair pair<int, int>
    #define MP(x, y) make_pair(x, y)
    #define fi first
    #define se second
    #define int long long 
    #define LL long long 
    #define ull unsigned long long 
    #define rg register 
    #define pt(x) printf("%d ", x);
    //#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1<<22, stdin), p1 == p2) ? EOF : *p1++)
    //char buf[(1 << 22)], *p1 = buf, *p2 = buf;
    //char obuf[1<<24], *O = obuf;
    //void print(int x) {if(x > 9) print(x / 10); *O++ = x % 10 + '0';}
    //#define OS  *O++ = ' ';
    using namespace std;
    //using namespace __gnu_pbds;
    const int MAXN = 1e6 + 10, INF = 1e9 + 10, mod = 1e9 + 7, BB = 32323;
    const double eps = 1e-9;
    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;
    struct Node {
        double a, b;
        bool operator < (const Node &rhs) const {
            return a == rhs.a ? b < rhs.b : a < rhs.a;
        }
    }P[MAXN], s1[MAXN], s2[MAXN];
    int t1 = 0, t2 = 0, ans[MAXN];
    double cross(Node x, Node y) {
    //    printf("%lf
    ", 1.0 * (y.b - x.b) / (x.a - x.b));
        return 1.0 * (y.b - x.b) / (x.a - y.a);
    }
    void Get() {
        sort(P + 1, P + N + 1);
        s1[++t1] = P[1];
        for(int i = 2; i <= N; i++) {
            if(t1 && P[i].a == s1[t1].a) t1--;
            while(t1 > 1 && cross(P[i], s1[t1]) <= cross(s1[t1], s1[t1 - 1])) t1--;
            s1[++t1] = P[i];
        }
        for(int i = 1; i <= N; i++) P[i].b = -P[i].b;
        sort(P + 1, P + N + 1);
        s2[++t2] = P[1];
        for(int i = 2; i <= N; i++) {
            if(t1 && P[i].a == s2[t2].a) t2--;
            while(t2 > 1 && cross(P[i], s2[t2]) <= cross(s2[t2], s2[t2 - 1])) t2--;
            s2[++t2] = P[i];
        }
    }
    int Query(Node p, int x) {
        return p.a * x * x + p.b * x;
    }
    void MakeAns() {
        for(int i = 1, c = 1; i <= BB; i++) {
            //printf("%lf
    ", cross(s1[c], s1[c + 1]));
            while(c < t1 && cross(s1[c], s1[c + 1]) <= (double)i) c++;
            ans[i + BB] = Query(s1[c], i);
        }
        for(int i = 1, c = 1; i <= BB; i++) {
            while(c < t2 && cross(s2[c], s2[c + 1]) <= (double)i) c++;
            ans[BB - i] = Query(s2[c], i);
        }
    }
    main() {
    //    freopen("a.in", "r", stdin);
        N = read(); int Q = read();
        for(int i = 1; i <= N; i++) P[i].a = read(), P[i].b = read();
        Get();
        MakeAns();
        while(Q--) {
            int x = read();
            printf("%lld
    ", ans[x + BB]);
        }
        return 0;
    }
    /*
    2 2 1
    1 1
    2 1 1
    */
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  • 原文地址:https://www.cnblogs.com/zwfymqz/p/9583183.html
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