[動態規劃]Tak and Cards
阿新 • • 發佈:2018-05-22
das 三次 span pan num nts com for integer
Constraints
1≤N≤50
1≤A≤50
1≤xi≤50
N,A,xi are integers.
Partial Score
200 points will be awarded for passing the test set satisfying 1≤N≤16.
N A
x1 x2 … xN
題目描述
Tak has N cards. On the i-th (1≤i≤N) card is written an integer xi. He is selecting one or more cards from these N cards, so that the average of the integers written on the selected cards is exactly A. In how many ways can he make his selection?Constraints
1≤N≤50
1≤A≤50
1≤xi≤50
Partial Score
200 points will be awarded for passing the test set satisfying 1≤N≤16.
輸入
The input is given from Standard Input in the following format:N A
x1 x2 … xN
輸出
Print the number of ways to select cards such that the average of the written integers is exactly A.樣例輸入
4 8
7 9 8 9
樣例輸出
5
提示
The following are the 5 ways to select cards such that the average is 8:
Select the 3-rd card.
Select the 1-st and 2-nd cards.
Select the 1-st and 4-th cards.
Select the 1-st, 2-nd and 3-rd cards.
Select the 1-st, 3-rd and 4-th cards.
#include <iostream> #include<cstdio> typedef long long ll; using namespace std; int a[55]; int sum[55]; ll dp[55][2505]; int main() { int n,A; scanf("%d%d",&n,&A); for(int i=1;i<=n;i++) {scanf("%d",&a[i]); sum[i]=sum[i-1]+a[i];} dp[0][0]=1; for(int k=1;k<=n;k++){ for(int i=k;i>=1;i--){ for(int j=sum[k];j>=a[k];j--){ dp[i][j]+=dp[i-1][j-a[k]]; } } } ll ans=0; for(int i=1;i<=n;i++) ans+=dp[i][i*A]; printf("%lld\n",ans); return 0; }
另外,關於動態規劃和遞推,我已經分不清了(#°Д°)
[動態規劃]Tak and Cards