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.
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.
The output should contains the smallest possible length of original sticks, one per line.
9 5 2 1 5 2 1 5 2 1 4 1 2 3 4 0
6 5
还是太弱了，参考了别人的代码。 这个题体现了剪枝的重要性。剪一刀（加一个限定条件）计算过程可以减少若干倍。
#include<stdio.h>#include<string.h>#include<algorithm>#define MAX_N 70using namespace std;int a[MAX_N];bool vis[MAX_N];int goal,sum,N;bool dfs(int now,int head,int cnt){ if(goal*cnt==sum) return true; for(int i=head;i<N;i++){ if(vis[i]||(i&&!vis[i-1]&&a[i]==a[i-1])) continue; if(now+a[i]==goal){ vis[i]=true; if(dfs(0,0,cnt+1)) return true; return vis[i]=false; } if(now+a[i]<goal){ vis[i]=true; if(dfs(now+a[i],i+1,cnt)) return true; vis[i]=false; if(!now) return false; } } return false;}bool cmp(int x,int y){return x>y;}int main(){ while(scanf("%d",&N)&&N!=0){ sum=0;int M=-1; for(int i=0;i<N;i++){ scanf("%d",&a[i]); M=max(a[i],M); sum+=a[i]; } sort(a,a+N,cmp); memset(vis,0,sizeof(vis)); for(goal=M;goal<=sum;goal++) if(sum%goal==0&&dfs(0,0,0)) break; printf("%d/n",goal); } return 0;}新闻热点
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