hdu 5533 Dancing Stars on Me（水）

解题思路

代码

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;
const int maxn = 105;

struct Point {
int x, y;
Point (int x = 0, int y = 0): x(x), y(y) {}

void read() { scanf("%d%d", &x, &y); }
bool operator == (const Point& u) const { return x == u.x && y == u.y; }
bool operator < (const Point& u) const { return x < u.x || (x == u.x && y < u.y); }

Point operator + (const Point& u) const { return Point(x + u.x, y + u.y); }
int operator * (const Point& u) const { return x * u.x + y * u.y; }
int operator ^ (const Point& u) const { return x * u.y - y * u.x; }
};

int N;
Point P[maxn];

bool judge () {
if (N != 4) return false;
vector<int> g;
g.clear();

for (int i = 0; i < N; i++) {
for (int j = i + 1; j < N; j++) {
int x = P[i].x - P[j].x;
int y = P[i].y - P[j].y;
g.push_back(x * x + y * y);
}
}
sort(g.begin(), g.end());
for (int i = 1; i < 4; i++)
if (g[i] != g[0]) return false;
return g[4] == g[5];
}

int main () {
int cas;
scanf("%d", &cas);
while (cas--) {
scanf("%d", &N);
for (int i = 0; i < N; i++) P[i].read();
printf("%s\n", judge() ? "YES" : "NO");
}
return 0;
}