POJ 3565 Ants

KM 模板题

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#include<queue>
using namespace std;

const int MAXN = 107;
const int INF = 1<<27;
const double eps = 1e-6;
struct KM {
	double dt[MAXN][MAXN];
	double lx[MAXN], ly[MAXN], slack[MAXN];
	int match[MAXN];
	int n;
	bool vx[MAXN], vy[MAXN];
	void init(int n) { this->n = n;}
	void add(int u, int v, double d) { dt[u][v] = d;}
	
	bool dfs(int u) {
		vx[u] = true;
		double tmp;
		for(int i = 1; i <= n; i++) {
			if(vy[i]) continue;
			tmp = lx[u] + ly[i] - dt[u][i];
			if(tmp < eps) {
				vy[i] = true;
				if(match[i] == -1 || dfs(match[i]))
				{
					match[i] = u;
					return true;
				}
			}
			else slack[i] = min(slack[i], tmp);
		}
		return false;
	}
	void km() {
		int i, j, k;
		memset(match, -1, sizeof(match));
		memset(ly, 0, sizeof(ly));
		for(i = 1; i <= n; i++){
			lx[i] = dt[i][1];
			for(j = 2; j <= n; j++) lx[i] = max(lx[i], dt[i][j]);
		}
		for(k = 1; k <= n; k++) {
			for(i = 1; i <= n; i++) slack[i] = INF;
			while(true) {
				memset(vx, 0, sizeof(vx));
				memset(vy, 0, sizeof(vy));
				if(dfs(k)) break;
				double nmin = INF;
				for(i = 1; i <= n; i++) {
					if( !vy[i]) nmin = min(nmin, slack[i]);
				}
				for(i = 1; i <= n; i++) {
					if(vx[i]) lx[i] -= nmin;
					if(vy[i]) ly[i] += nmin;
					else slack[i] -= nmin;
				}
			}
		}
	}
}km;

int x[2][MAXN], y[2][MAXN];
int link[MAXN];

double dist(int x1, int y1, int x2, int y2) {
	return sqrt( (double)(x1-x2)*(x1-x2) + (y1-y2)*(y1-y2) );
}

int main() {
	int n, i, j;
	while(~scanf("%d", &n)){
		km.init(n);
		for(i = 1; i <= n; i++) scanf("%d%d", &x[0][i], &y[0][i]);
		for(i = 1; i <= n; i++) scanf("%d%d", &x[1][i], &y[1][i]);
		for(i = 1; i <= n; i++) {
			for(j = 1; j <= n; j++) {
				km.add(i, j, -dist(x[0][i], y[0][i], x[1][j], y[1][j]));
			}
		}
		km.km();
		for(i = 1; i <= n; i++) {
			for(j = 1; j <= n; j++) if(km.match[j] == i) {
				printf("%d\n", j);
			}
		}
	}
	return 0;
}