BYSBZ 2748(音量调节-01背包）
一定要读题啊！！
这题说的是——每次一定换，没说前后不能到一个音量。
#include<cstdio>#include<cstring>#include<queue>#include<cmath>#include<cstdlib>#include<iostream>#include<functional>#include<algorithm>#include<stack>using namespace std;#define MAXN (50 + 10)#define MAXMAXLEVEL (1000+1)int n,start,maxlevel,a[MAXN];bool f[MAXN][MAXMAXLEVEL];int main(){// freopen("changingsounds.in","r",stdin);// freopen("changingsounds.out","w",stdout); memset(f,0,sizeof(f)); scanf("%d%d%d",&n,&start,&maxlevel); for (int i=1;i<=n;i++) scanf("%d",&a[i]); f[0][start]=1; for (int i=1;i<=n;i++) for (int j=0;j<=maxlevel;j++) { f[i][j]=j-a[i]>=0? f[i-1][j-a[i]] : 0; f[i][j]=j+a[i]<=maxlevel? f[i-1][j+a[i]]||f[i][j] : f[i][j]; } int ans=maxlevel; while (ans>=0&&!f[n][ans]) ans--; cout<<ans<<endl; // while (1); return 0;}