UVa 1411 Ants(KM)

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题目链接：UVa 1411 Ants

汝佳大神的版~以后KM就用这个了。。

最佳匹配是不会有交点的，证明白书上有~

// LA4043 Ants// Rujia Liu#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const int maxn = 100 + 10;const double INF = 1e30;int n;double W[maxn][maxn];double Lx[maxn], Ly[maxn];   // 顶标int left[maxn];          // left[i]为右边第i个点的匹配点编号bool S[maxn], T[maxn];   // S[i]和T[i]为左/右第i个点是否已标记bool eq(double a, double b) {  return fabs(a-b) < 1e-9;}bool match(int i){  S[i] = true;  for(int j = 1; j <= n; j++) if (eq(Lx[i]+Ly[j], W[i][j]) && !T[j]){    T[j] = true;    if (!left[j] || match(left[j])){      left[j] = i;      return true;    }  }  return false;}void update(){  double a = INF;  for(int i = 1; i <= n; i++) if(S[i])    for(int j = 1; j <= n; j++) if(!T[j])      a = min(a, Lx[i]+Ly[j] - W[i][j]);  for(int i = 1; i <= n; i++) {    if(S[i]) Lx[i] -= a;    if(T[i]) Ly[i] += a;  }}void KM() {  for(int i = 1; i <= n; i++) {    left[i] = Lx[i] = Ly[i] = 0;    for(int j = 1; j <= n; j++)      Lx[i] = max(Lx[i], W[i][j]);  }  for(int i = 1; i <= n; i++) {    for(;;) {      for(int j = 1; j <= n; j++) S[j] = T[j] = 0;      if(match(i)) break; else update();    }  }}int main(){  int kase = 0;  while(scanf("%d", &n) == 1) {    if(++kase > 1) printf("\n");    int x1[maxn], y1[maxn], x2[maxn], y2[maxn];    for(int i = 1; i <= n; i++) scanf("%d%d", &x1[i], &y1[i]);    for(int i = 1; i <= n; i++) scanf("%d%d", &x2[i], &y2[i]);    for(int i = 1; i <= n; i++) // ant colony      for(int j = 1; j <= n; j++) // apple tree        W[j][i] = -sqrt((double)(x1[i]-x2[j])*(x1[i]-x2[j]) + (double)(y1[i]-y2[j])*(y1[i]-y2[j]));    KM(); // 最大权匹配    for(int i = 1; i <= n; i++) printf("%d\n", left[i]);  }  return 0;}

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