母函式——秤砣問題——The Balance
Now you are asked to measure a dose of medicine with a balance and a number of weights. Certainly it is not always achievable. So you should find out the qualities which cannot be measured from the range [1,S]. S is the total quality of all the weights.
Input
The input consists of multiple test cases, and each case begins with a single positive integer N (1<=N<=100) on a line by itself indicating the number of weights you have. Followed by N integers Ai (1<=i<=N), indicating the quality of each weight where 1<=Ai<=100.
Output
For each input set, you should first print a line specifying the number of qualities which cannot be measured. Then print another line which consists all the irrealizable qualities if the number is not zero.
Sample Input
3 1 2 4 3 9 2 1
Sample Output
0 2 4 5
題意:給你一些秤砣,找出在不超過重質量的情況下,哪些重量是稱不出來的
考慮一個特殊的情況: 給你一個1,一個2,要想稱出1,很明顯放一個重量為1的即可,但是天平左邊放1,右邊放2,同樣可以稱出1;
可以稱出的質量還可得到這樣一個式子 ; m1,m2 分別為兩個秤砣重量;
#include<bits/stdc++.h> using namespace std; typedef long long ll; const int maxn=20000; int n; int a[maxn]; int t[maxn]; int v[maxn]; int main() { while(scanf("%d",&n)!=EOF) { int s=0; memset(t,0,sizeof t); memset(v,0,sizeof v); for(int i=1;i<=n;++i) scanf("%d",&a[i]),s+=a[i]; v[0]=1; v[a[1]]=1; for(int i=2;i<=n;++i) { for(int j=0;j<=s;++j) for(int k=0;k+j<=s&&k<=a[i];k+=a[i]) { t[abs(j-k)] += v[j]; t[j+k]+=v[j]; } for(int j=0;j<=s;++j) { v[j]=t[j]; t[j]=0; } } int cnt=0; for(int i=0;i<=s;++i) if(v[i]==0) ++cnt; cout<<cnt<<endl; if(cnt==0) continue; else { for(int i=0;i<=s;++i) { if(!v[i]) { printf("%d",i); --cnt; if(cnt) printf(" "); else puts(""); } } } } }