File size: 2,073 Bytes
e1191aa | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | #include <cstdio>
#include <cstring>
#include <vector>
using namespace std;
#define MAXN 700
typedef unsigned char uch;
typedef unsigned int u32;
//
// Hash Map
//
#define HASHB 4096
const size_t KeySz = sizeof(int) * 2;
struct HM {
struct Key {
int d[2];
Key(int *D) { memcpy(d, D, KeySz); }
bool operator==(const Key &x) const {
return memcmp(d, x.d, KeySz) == 0; }
};
struct KV {
Key k; int v;
KV(const Key &K, int V) : k(K), v(V) {}
};
typedef vector<KV> KVV; KVV b[HASHB];
u32 fnv_hash(const Key &k, int len) const {
uch *p = reinterpret_cast<uch*>(const_cast<int*>(k.d));
u32 h = 2166136261U;
for (int i = 0; i < len; ++i) h = (h * 16777619U) ^ p[i];
return h;
}
int add(const Key &k) {
int i = fnv_hash(k, KeySz) % HASHB;
for (int j = 0, J = b[i].size(); j < J; ++j)
if (b[i][j].k == k)
return ++b[i][j].v;
b[i].push_back(KV(k, 2));
return 2;
return true;
}
};
template<typename T>
T gcd(T a, T b) { for (T c = a%b; c != 0; a=b,b=c,c=a%b); return b; }
int n;
int pts[MAXN][2];
int solve()
{
if (n <= 2) return n;
int ans = 0;
int m[2]; // slope, as a rational number
for (int i = 0; i < n; ++i) {
HM hm;
for (int j = i + 1; j < n; ++j) {
if (pts[i][0] == pts[j][0])
m[0] = m[1] = 0;
else {
m[0] = pts[j][1] - pts[i][1];
m[1] = pts[j][0] - pts[i][0];
int g = gcd(m[0], m[1]);
m[0] /= g;
m[1] /= g;
}
int coll = hm.add(HM::Key(m));
if (coll > ans) ans = coll;
}
}
return ans;
}
int main()
{
int T;
scanf("%d", &T);
int ncase = 0;
while (T--) {
scanf("%d", &n);
for (int i = 0; i < n; ++i)
scanf("%d%d", &pts[i][0], &pts[i][1]);
printf("Case %d: %d\n", ++ncase, solve());
}
return 0;
}
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