Sticks
Time Limit:1000MSMemory Limit:10000K
Total Submissions:127727Accepted:29912
Description
George took sticks of the same length and cut them randomly until all parts became at most 50 units long. Now he wants to return sticks to the original state, but he forgot how many sticks he had originally and how long they were originally. Please help him and design a program which computes the smallest possible original length of those sticks. All lengths expressed in units are integers greater than zero.
Input
The input contains blocks of 2 lines. The first line contains the number of sticks parts after cutting, there are at most 64 sticks. The second line contains the lengths of those parts separated by the space. The last line of the file contains zero.
Output
The output should contains the smallest possible length of original sticks, one per line.
Sample Input
95 2 1 5 2 1 5 2 141 2 3 40
Sample Output
65
题意：告诉n个小木条，问能组成几个等长的木棍，并且让长度最小。
分析：神剪枝问题，，有与没有天壤之别，
#include <iostream>#include <stdio.h>#include <string>#include <cstring>#include <algorithm>#include <cmath>#define N 100009using namespace std;int cmp(int a,int b){return a>b;}int sum,mmin;int flag;int n;int vis[N];int a[N];int cnt;int len;void dfs(int p,int num,int x){if(flag) return;if(num==cnt){flag=1;return;}if(x==len)dfs(0,num+1,0);for(int i=p;i<n;i++){if(vis[i]) continue;if( (x+a[i])>len) continue;vis[i]=1;dfs(i+1,num,x+a[i]);vis[i]=0;if(flag) return;//if(x==0||x+a[i]==len)//神剪枝，有就16毫秒，没有就是TLE//return;//具体理解为if(x==0)//如果第一个木棒都没有添加，说明有问题return;if(x+a[i]==len)//如果现在本来应该成功，应该进入递归变为0，却失败，说明有问题return;}}int main(){while(scanf("%d",&n),n){sum=0;mmin=0;for(int i=0;i<n;i++){scanf("%d",&a[i]);mmin=max(mmin,a[i]);sum+=a[i];}sort(a,a+n,cmp);memset(vis,0,sizeof vis);int ans=sum;for(len=mmin;len<=sum;len++){if(sum%len) continue;cnt=sum/len;flag=0;dfs(0,0,0);if(flag){ans=len;break;}}printf("%d\n",ans);}return 0;}
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人之所以有一张嘴，而有两只耳朵，原因是听的要比说的多一倍。
