WIKIOI 2941 西游记 题解与分析

【题目链接】：http://www.wikioi.com/problem/2941/

【分析】：详见http://blog.csdn.net/csyzcyj/article/details/17332883

【代码】：

#include<stdio.h>#include<string.h>#include<stdlib.h>#include<algorithm>#include<iostream>#include<vector>#include<bitset>using namespace std;#define MAX 20#define MAXN 65537#define IMAX 2147483647long long N,map[MAX][MAX],f[MAXN][MAX],state[MAX][MAXN],num[MAXN];long long ans=IMAX;void floyed(){      for(int k=0;k<=N;k++)            for(int i=0;i<=N;i++)                  for(int j=0;j<=N;j++)                        if(map[i][j]>map[i][k]+map[k][j])                              map[i][j]=map[i][k]+map[k][j];      }void work(){      for(int i=0;i<=(1<<(N+1));i++)            for(int j=0;j<=N+1;j++)                  f[i][j]=IMAX;      for(int i=0;i<(1<<N);i++)      {            int tot=0;            for(int j=0;j<N;j++)                  if(((1<<j)&i))                       tot++;            state[tot][++num[tot]]=i;                  }      for(int i=1;i<=N;i++)            f[(1<<(i-1))][i]=map[0][i];      for(int i=1;i<N;i++)            for(int l=1;l<=num[i];l++)                  for(int j=1;j<=N;j++)                  {                        if(((1<<(j-1))&state[i][l]))                             for(int k=1;k<=N;k++)                             {                                     if(!((1<<(k-1))&state[i][l]))                                             f[(state[i][l]+(1<<(k-1)))][k]=min(f[(state[i][l]+(1<<(k-1)))][k],f[state[i][l]][j]+map[j][k]);                             }                  }}int main(){      //freopen("input.in","r",stdin);  //freopen("output.out","w",stdout);      scanf("%lld",&N);   for(int i=0;i<=N;i++)            for(int j=0;j<=N;j++)                  scanf("%lld",&map[i][j]);       floyed();      work();      for(int i=1;i<=N;i++)            ans=min(ans,f[(1<<N)-1][i]+map[i][0]);      printf("%lld\n",ans);      return 0;}

 

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