BZOJ 1492 Cash（CDQ分治论文题）

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CDQ分治论文题
#include<cstdio>#include<cstring>#include<cmath>#include<cstdlib>#include<iostream>#include<algorithm>#include<vector>#include<map>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<ctime>#define eps 1e-9#define LL long long#define pii pair<int, int>//#pragma comment(linker, "/STACK:1024000000,1024000000")using namespace std;const int maxn = 100000 + 1000;int n;double ans[maxn];struct Point {double a, b, r;double x, y, k;int id;bool operator < (const Point& A) const {return x < A.x;}} p[maxn], t[maxn];int S[maxn];double getK(int a, int b) {if(!b) return 1e-20;if(fabs(p[a].x-p[b].x) < eps) return 1e20;return (p[b].y-p[a].y) / (p[b].x-p[a].x);}bool cmp(const Point A, const Point B) {return A.k > B.k;}void CDQ(int L, int R) {if(L == R) {ans[L] = max(ans[L], ans[L-1]);p[L].y = ans[L]/(p[L].r*p[L].a+p[L].b);p[L].x = p[L].y*p[L].r;return;}int mid = (L+R) >> 1;int l1 = L, l2 = mid + 1;for(int i = L; i <= R; i++) {if(p[i].id > mid) t[l2++] = p[i];else t[l1++] = p[i];}for(int i = L; i <= R; i++) p[i] = t[i];CDQ(L, mid);int top = 0, pos = 1;for(int i = L; i <= mid; i++) {while(top>1 && getK(S[top-1], S[top])<getK(S[top-1], i)+eps)top--;S[++top] = i;}for(int i = mid+1; i <= R; i++) {while(pos<top && getK(S[pos], S[pos+1])+eps>p[i].k) pos++;ans[p[i].id] = max(ans[p[i].id], p[i].a*p[S[pos]].x+p[i].b*p[S[pos]].y);}CDQ(mid+1, R);merge(p+L, p+mid+1, p+mid+1, p+R+1, t+L);for(int i = L; i <= R; i++) p[i] = t[i];} int main() {    //freopen("input.txt", "r", stdin);scanf("%d%lf", &n, &ans[0]);for(int i = 1; i <= n; i++) {scanf("%lf%lf%lf", &p[i].a, &p[i].b, &p[i].r);p[i].k = -p[i].a/p[i].b;p[i].id = i;}sort(p+1, p+n+1, cmp);CDQ(1, n);printf("%.3lf", ans[n]);    return 0;}
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