POJ 1011 Sticks

来源：互联网发布：手机变平板软件编辑：程序博客网时间：2024/05/16 01:27

DFS

题意是让你把这些木棍组合成长度相等的一些木棍。要求长度最短。

#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;int a[65],n,sum,ans;bool v[65],ok;bool cmpa(int a,int b){    return a>b;}bool dfs(int num,int need,int total){    int i;    if(need==0)    {        if(total==sum/ans-2)return 1;        for(i=0;v[i];i++);        v[i]=1;        if(dfs(i+1,ans-a[i],total+1))return 1;        v[i]=0;        return 0;    }    else    {        if(num>=n-1)return 0;        for(i=num;i<n;i++)        {            if(a[i]==a[i-1]&&!v[i-1])            continue;            if(!v[i]&&a[i]<=need)            {                v[i]=1;                if(dfs(i,need-a[i],total))return 1;                v[i]=0;            }        }        return 0;    }}int main(){    while(scanf("%d",&n),n)    {        sum=ans=0;        for(int i=0;i<n;i++)        scanf("%d",&a[i]),sum+=a[i];        sort(a,a+n,cmpa);        memset(v,0,sizeof(v));        ok=0;        for(ans=a[0];ans<=sum/2;ans++)        {            if(sum%ans==0)            {                v[0]=1;                if(dfs(0,ans-a[0],0))                {printf("%d\n",ans);ok=1;break;}            }        }        if(!ok)        printf("%d\n",sum);    }    return 0;}

还有更强大的剪枝版本的：

#include<cstdio>#include<cstring>#include<cstring>#define MAX 64int s[MAX],vis[MAX],n,len,sum;void input(){   int i,j,temp;    sum = 0;       for(i=0;i<n;i++)         {            scanf("%d ",&s[i]);            sum+=s[i];         }      for(i=1;i<n;i++)       for(j=0;j<n-i;j++)       {           if(s[j]<s[j+1])          {           temp = s[j];           s[j] = s[j+1];           s[j+1] = temp;          }       }}bool dfs(int now_len,int i,int count){    if((count+1)*len==sum)    {        return true;    }    for(int k= i;k<n;k++)    {       if(vis[k]) continue;       if(k&&!vis[k-1]&&s[k]==s[k-1]) continue;       if(s[k]+now_len>len) continue;       if(now_len+s[k]==len)       {           vis[k]=1;           bool result = dfs(0,0,count+1);           vis[k]=0;            return result;       }       else if(now_len==0)       {           vis[k]=1;           bool result = dfs(s[k],k+1,count);           vis[k]= 0;           return result;       }       else if(now_len+s[k]<len)       {           vis[k] = 1;           bool result = dfs(s[k]+now_len,k+1,count);           vis[k] = 0;           if(result)           return true;       }    }    return false;}int main(){    while(scanf("%d",&n),n)    {       input();       for(len=s[0];len<=sum;len++)       {           if(sum%len) continue;           memset(vis,0,sizeof(vis));           if(dfs(0,0,0))           break;       }       printf("%d\n",len);    }}

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