HDU3722 Card Game（KM最小费用圈覆盖）

题意：告诉纸牌之间的边的权重时第一个字符串逆序，和第二个字符串的最长公共前缀，预处理下这个权重。在KM下即可

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<set>
#include<map>
#include<string>
#include<cstring>
#include<stack>
#include<queue>
#include<vector>
#include<cstdlib>
#define lson (rt<<1),L,M
#define rson (rt<<1|1),M+1,R
#define M ((L+R)>>1)
#define cl(a,b) memset(a,b,sizeof(a));
#define LL long long
#define P pair<int,int>
#define X first
#define Y second
#define pb push_back
#define fread(zcc)  freopen(zcc,"r",stdin)
#define fwrite(zcc) freopen(zcc,"w",stdout)
using namespace std;
const int maxn=205;
const int inf=1<<28;

int w[maxn][maxn];
int linker[maxn],lx[maxn],ly[maxn],slack[maxn];
bool visx[maxn],visy[maxn];
int nx,ny;

bool dfs(int x){
    visx[x]=true;
    for(int i=0;i<ny;i++){
        if(visy[i])continue;
        int tmp=lx[x]+ly[i]-w[x][i];
        if(tmp==0){
            visy[i]=true;
            if(linker[i]==-1||dfs(linker[i])){
                linker[i]=x;
                return true;
            }
        }else if(slack[i]>tmp){
            slack[i]=tmp;
        }
    }
    return false;
}
int km(){
    cl(linker,-1);
    cl(ly,0);
    for(int i=0;i<nx;i++){
        lx[i]=-inf;
        for(int j=0;j<ny;j++)if(w[i][j]>lx[i]){lx[i]=w[i][j];}
    }
    for(int x=0;x<nx;x++){
        fill(slack,slack+ny+1,inf);
        while(true){
            cl(visx,false);
            cl(visy,false);
            if(dfs(x))break;

            int d=inf;
            for(int i=0;i<ny;i++)if(!visy[i]&&slack[i]<d){
                d=slack[i];
            }
            for(int i=0;i<nx;i++)if(visx[i])lx[i]-=d;
            for(int i=0;i<ny;i++)if(visy[i])ly[i]+=d;
            else slack[i]-=d;
        }
    }
    int ans=0;
    bool ok=false;
    for(int i=0;i<ny;i++)if(linker[i]!=-1){
        ans+=w[linker[i]][i];
        if(w[linker[i]][i]==-inf)ok=true;///
    }
    if(ok)return 1;
    return ans;
}
char a[maxn][1005];
int getprefix(char *s,char *t){
    int n=strlen(s);
    int m=strlen(t);
    int i=n-1,j=0;
    int cnt=0;
    while(i>=0&&j<m){
        if(s[i]==t[j])cnt++;
        else break;
        i--;j++;
    }
    return cnt;
}
int main(){
    int n;
    while(~scanf("%d",&n)){
        for(int i=0;i<n;i++){
            scanf("%s",&a[i]);
        }
        nx=ny=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<n;j++){
                if(i==j)w[nx][j]=0;
                else {
                    w[nx][j]=getprefix(a[i],a[j]);
                }
            }
            nx++;
        }
        ny=n;
        //printf("nx = %d, ny = %d\n",nx,ny);
        printf("%d\n",km());
    }
    return 0;
}