1 #include<cstdio> 2 #include<cmath> 3 #include<cstring> 4 #include<algorithm> 5 #define MAXN 5000 6 #define MAXM 60 7 #define INF 0x7FFFFFFF 8 using namespace std; 9 int n, m, size; 10 int L[MAXN], R[MAXN], U[MAXN], D[MAXN]; 11 int H[MAXM], S[MAXM], C[MAXN], a[MAXN]; 12 int dis[MAXM][MAXM]; 13 bool vis[MAXM]; 14 struct Point { 15 int x, y; 16 }; 17 Point p[MAXM]; 18 int DIS(int i, int j) { 19 int x, y; 20 x = p[i].x - p[j].x; 21 y = p[i].y - p[j].y; 22 return x * x + y * y; 23 } 24 void Init() { 25 int i; 26 for (i = 0; i <= n; i++) { 27 R[i] = i + 1; 28 L[i + 1] = i; 29 U[i] = D[i] = i; 30 S[i] = 0; 31 H[i] = -1; 32 } 33 R[n] = 0; 34 size = n + 1; 35 } 36 void Link(int r, int c) { 37 U[size] = c; 38 D[size] = D[c]; 39 U[D[c]] = size; 40 D[c] = size; 41 if (H[r] < 0) 42 H[r] = L[size] = R[size] = size; 43 else { 44 L[size] = H[r]; 45 R[size] = R[H[r]]; 46 L[R[H[r]]] = size; 47 R[H[r]] = size; 48 } 49 S[c]++; 50 C[size++] = c; 51 } 52 int A() { 53 int i, j, k, res; 54 memset(vis, false, sizeof(vis)); 55 for (res = 0, i = R[0]; i; i = R[i]) { 56 if (vis[i]) 57 continue; 58 res++; 59 for (j = D[i]; j != i; j = D[j]) { 60 for (k = R[j]; k != j; k = R[k]) 61 vis[C[k]] = true; 62 } 63 } 64 return res; 65 } 66 void Remove(int c) { 67 int i; 68 for (i = D[c]; i != c; i = D[i]) { 69 L[R[i]] = L[i]; 70 R[L[i]] = R[i]; 71 } 72 } 73 void Resume(int c) { 74 int i; 75 for (i = D[c]; i != c; i = D[i]) 76 L[R[i]] = R[L[i]] = i; 77 } 78 bool Dance(int now) { 79 if (now + A() > m) 80 return false; 81 if (R[0] == 0) 82 return true; 83 int i, j, temp, c; 84 for (temp = INF, i = R[0]; i; i = R[i]) { 85 if (S[i] < temp) { 86 temp = S[i]; 87 c = i; 88 } 89 } 90 for (i = D[c]; i != c; i = D[i]) { 91 Remove(i); 92 for (j = R[i]; j != i; j = R[j]) 93 Remove(j); 94 if (Dance(now + 1)) 95 return true; 96 for (j = L[i]; j != i; j = L[j]) 97 Resume(j); 98 Resume(i); 99 } 100 return false; 101 } 102 bool OK(int mid) { 103 int i, j; 104 Init(); 105 for (i = 1; i <= n; i++) { 106 for (j = 1; j <= n; j++) { 107 if (dis[i][j] <= mid) 108 Link(i, j); 109 } 110 } 111 return Dance(0); 112 } 113 int main() { 114 int T, i, j, cnt; 115 int high, low, mid; 116 scanf("%d", &T); 117 while (T--) { 118 scanf("%d%d", &n, &m); 119 for (i = 1; i <= n; i++) 120 scanf("%d%d", &p[i].x, &p[i].y); 121 for (cnt = 0, i = 1; i <= n; i++) { 122 for (j = i; j <= n; j++) 123 a[cnt++] = dis[i][j] = dis[j][i] = DIS(i, j); 124 } 125 sort(a, a + cnt); 126 cnt = unique(a, a + cnt) - a; 127 for (low = 0, high = cnt; low < high;) { 128 mid = (low + high) >> 1; 129 if (OK(a[mid])) 130 high = mid; 131 else 132 low = mid + 1; 133 } 134 printf("%lf\n", sqrt((double) a[low])); 135 } 136 return 0; 137 }
