Poj--2536（二分图最大匹配）
2014-11-04 17:53:19
思路：二分图最大匹配经典模型，根据每个地鼠能到的洞建有向边。
1 /************************************************************************* 2 > File Name: 2536.cpp 3 > Author: Nature 4 > Mail: 564374850@qq.com 5 > Created Time: Tue 04 Nov 2014 05:44:15 PM CST 6 ************************************************************************/ 7 8 #include <cstdio> 9 #include <cstring> 10 #include <cstdlib> 11 #include <cmath> 12 #include <vector> 13 #include <map> 14 #include <set> 15 #include <stack> 16 #include <queue> 17 #include <iostream> 18 #include <algorithm> 19 using namespace std; 20 #define lp (p << 1) 21 #define rp (p << 1|1) 22 #define getmid(l,r) (l + (r - l) / 2) 23 #define MP(a,b) make_pair(a,b) 24 typedef long long ll; 25 const int INF = 1 << 30; 26 const double eps = 1e-8; 27 const int maxn = 110; 28 29 int n,m,s,v; 30 double gx[maxn],gy[maxn],hx[maxn],hy[maxn]; 31 int first[maxn],next[maxn * maxn],ver[maxn * maxn],ecnt; 32 int used[maxn],mat[maxn]; 33 34 void Init(){ 35 memset(first,-1,sizeof(first)); 36 ecnt = 0; 37 } 38 39 void Add_edge(int u,int v){ 40 next[++ecnt] = first[u]; 41 ver[ecnt] = v; 42 first[u] = ecnt; 43 } 44 45 double Dis(double x1,double y1,double x2,double y2){ 46 return sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)); 47 } 48 49 void Build_graph(){ 50 double d = 1.0 * s * v; 51 for(int i = 1; i <= n; ++i){ 52 for(int j = 1; j <= m; ++j){ 53 if(d - Dis(gx[i],gy[i],hx[j],hy[j]) > eps){ 54 Add_edge(i,j); 55 } 56 } 57 } 58 } 59 60 bool find(int p){ 61 for(int i = first[p]; i != -1; i = next[i]){ 62 int v = ver[i]; 63 if(used[v] == 0){ 64 used[v] = 1; 65 if(mat[v] == 0 || find(mat[v])){ 66 mat[v] = p; 67 return true; 68 } 69 } 70 } 71 return false; 72 } 73 74 int Hungary(){ 75 int ans = 0; 76 memset(mat,0,sizeof(mat)); 77 for(int i = 1; i <= n; ++i){ 78 memset(used,0,sizeof(used)); 79 if(find(i)) ++ans; 80 } 81 return ans; 82 } 83 84 int main(){ 85 while(scanf("%d%d%d%d",&n,&m,&s,&v) != EOF){ 86 Init(); 87 for(int i = 1; i <= n; ++i) 88 scanf("%lf%lf",&gx[i],&gy[i]); 89 for(int i = 1; i <= m; ++i) 90 scanf("%lf%lf",&hx[i],&hy[i]); 91 Build_graph(); 92 printf("%d\n",n - Hungary()); 93 } 94 return 0; 95 }
