学步园

精度问题卡死我了。

如果直接在括号里加-1.0*ans/(2*n)的话，被WA，而要转换为正数之后才可以AC。可能是POJ编译器的问题吧。

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <string>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <map>
using namespace std;

const int maxn = 30;
const int INF = 0x3f3f3f3f;

int n, m;

int W[maxn][maxn];
int Lx[maxn], Ly[maxn];

int Left[maxn];
bool S[maxn], T[maxn];

bool match(int i)
{
    S[i] = 1;
    for(int j = 1; j <= m; j++) if(Lx[i]+Ly[j] == W[i][j] && !T[j])
    {
        T[j] = 1;
        if(!Left[j] || match(Left[j]))
        {
            Left[j] = i;
            return 1;
        }
    }
    return 0;
}

void update()
{
    int a = INF;
    for(int i = 1; i <= n; i++) if(S[i])
    for(int j = 1; j <= m; 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;
    }
    for(int j = 1; j <= m; j++)
    {
        if(T[j]) Ly[j] += a;
    }
}

void KM()
{
    memset(Left, 0, sizeof(Left));
    memset(Lx, 0, sizeof(Lx));
    memset(Ly, 0, sizeof(Ly));
    
    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= m; j++)
            Lx[i] = max(Lx[i], W[i][j]);
    }
    for(int i = 1; i <= n; i++)
    {
        for(;;)
        {
            for(int j = 1; j <= m; j++) S[j] = T[j] = 0;
            if(match(i)) break; else update();
        }
    }
}

inline void readint(int &x)
{
    char c;
    c = getchar();
    while(!isdigit(c)) c = getchar();
    
    x = 0;
    while(isdigit(c)) x = x*10+c-'0', c = getchar();
}

inline void writeint(int x)
{
    if(x > 9) writeint(x/10);
    putchar(x%10+'0');
}

int Su[maxn][maxn], Em[maxn][maxn];

int N;

void read_case()
{
	scanf("%d", &N);
	n = m = N;
	
	memset(Em, 0, sizeof(Em));
	memset(Su, 0, sizeof(Su));
	for(int i = 1; i <= n; i++)
	for(int j = 1; j <= n; j++)
	{
		int q;
		scanf("%d", &q);
		W[q][i] -= (j-1);
	}
	
	for(int i = 1; i <= n; i++)
	for(int j = 1; j <= n; j++)
	{
		int q;
		scanf("%d", &q);
		W[i][q] -= (j-1);
	}
}

int times;
int ans;
int count2;
bool vis[maxn];

void dfs(int dep, int sum)
{
	if(sum < ans) return ;
	if(dep > n)
	{
		if(ans != sum) return ;
		printf("Best Pairing %d\n", ++count2);
		for(int i = 1; i <= n; i++)
			printf("Supervisor %d with Employee %d\n", i, Left[i]);
	}
	else for(int i = 1; i <= n; i++) if(!vis[i])
	{
		vis[i] = 1;
		Left[dep] = i;
		dfs(dep+1, sum+W[dep][i]);
		vis[i] = 0;
	}
}

void output()
{
	ans *= -1;
	printf("Data Set %d, Best average difference: %.6lf\n", ++times, (double)ans/(2*n));
	ans *= -1;
	count2 = 0;
	memset(vis, 0, sizeof(vis));
	
	dfs(1, 0);
	printf("\n");
}

void solve()
{
	memset(W, 0, sizeof(W));
	read_case();
	
	KM();
	
	ans = 0;
	for(int i = 1; i <= n; i++) if(Left[i]) ans += W[Left[i]][i];
	
	memset(vis, 0, sizeof(vis));
	output();
}

int main()
{
	int T;
	times = 0;
	for(readint(T); T > 0; T--)
	{
		solve();
	}
	return 0;
}