【HDU】3656 Fire station

  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 }