OJ-Problems-Source/HDOJ/5473_autoAC.cpp

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#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long ll;
struct Point {
ll x, y;
Point(ll x = 0, ll y = 0): x(x), y(y) {}
void read() { scanf("%lld%lld", &x, &y); }
bool operator < (const Point& u) const { return x < u.x || (x == u.x && y < u.y); }
bool operator == (const Point& u) const { return !(*this < u) && !(u < *this); }
bool operator != (const Point& u) const { return !(*this == u); }
bool operator > (const Point& u) const { return u < *this; }
bool operator <= (const Point& u) const { return *this < u || *this == u; }
bool operator >= (const Point& u) const { return *this > u || *this == u; }
Point operator + (const Point& u) { return Point(x + u.x, y + u.y); }
Point operator - (const Point& u) { return Point(x - u.x, y - u.y); }
Point operator * (const double u) { return Point(x * u, y * u); }
Point operator / (const double u) { return Point(x / u, y / u); }
ll operator ^ (const Point& u) { return x*u.y - y*u.x; }
};
typedef Point Vector;
ll Cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }
ll getArea (Point* p, int n) {
ll ret = 0;
for (int i = 0; i < n-1; i ++)
ret += Cross(p[i]-p[0], p[i+1]-p[0]);
return ret < 0 ? -ret : ret;
}
int getConvexHull (Point* p, int n, Point* ch) {
sort(p, p + n);
int m = 0;
for (int i = 0; i < n; i++) {
while (m > 1 && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-1]) <= 0) m--;
ch[m++] = p[i];
}
int k = m;
for (int i = n-2; i >= 0; i--) {
while (m > k && Cross(ch[m-1]-ch[m-2], p[i]-ch[m-1]) <= 0) m--;
ch[m++] = p[i];
}
if (n > 1) m--;
return m;
}
const int maxn = 105;
int N, K;
ll dp[maxn][maxn];
Point P[maxn], Q[maxn];
ll solve () {
ll allarea = getArea(P, N);
if (K >= N) return allarea;
ll ret = 0;
bool vis[maxn];
memset(vis, 0, sizeof(vis));
int ti = min(5 * (N / K), N);
for (int t = 0; t < ti; t++) {
int s = rand() % N;
while (vis[s]) s = rand() % N;
vis[s] = 1;
memset(dp, 0, sizeof(dp));
dp[0][0] = allarea;
for (int i = 1; i <= N; i++) {
int u = (i + s) % N;
ll sum = 0;
for (int j = i-1; j >= 0; j--) {
int v = (j + s) % N;
int p = (v + 1) % N;
ll tmp = ((P[p]-P[u])^(P[v]-P[u]));
if (tmp < 0) tmp = -tmp;
sum += tmp;
for (int x = K; x > 0; x--)
dp[i][x] = max(dp[i][x], dp[j][x-1]-sum);
}
}
ret = max(ret, dp[N][K]);
}
return ret;
}
int main () {
int cas;
scanf("%d", &cas);
srand((int)time(NULL));
for (int kcas = 1; kcas <= cas; kcas++) {
scanf("%d%d", &N, &K);
for (int i = 0; i < N; i++) Q[i].read();
N = getConvexHull(Q, N, P);
printf("Case #%d: %lld\n", kcas, solve());
}
return 0;
}