hdu 2955 水题却wa几次值得反思

#include<iostream>#include<cstring>#include<algorithm>#include<cstdio>#include<vector>#include<sstream>#include<string>#include<climits>#include<stack>#include<set>#include<bitset>#include<cmath>#include<deque>#include<map>#include<queue>#define iinf 0x7f7f7f7f#define linf 1000000000000000000LL#define dinf 1e200#define eps 1e-11#define all(v) (v).begin(),(v).end()#define sz(x)  x.size()#define pb push_back#define mp make_pair#define lng long long#define sqr(a) ((a)*(a))#define pii pair<int,int>#define pll pair<lng,lng>#define pss pair<string,string>#define pdd pair<double,double>#define X first#define Y second#define pi 3.14159265359#define ff(i,xi,n) for(int i=xi;i<=(int)(n);++i)#define ffd(i,xi,n) for(int i=xi;i>=(int)(n);--i)#define ffl(i,r) for(int i=head[r];i!=-1;i=edge[i].next)#define cc(i,j) memset(i,j,sizeof(i))#define two(x)          ((lng)1<<(x))#define lson l , mid , rt << 1#define rson mid + 1 , r , rt << 1 | 1#define mod  1000000007#define pmod(x,y) (x%y+y)%yusing namespace std;typedef vector<int>  vi;typedef vector<string>  vs;template<class T> inline void checkmax(T &x,T y){if(x<y) x=y;}template<class T> inline void checkmin(T &x,T y){if(x>y) x=y;}template<class T> inline T Min(T x,T y){return (x>y?y:x);}template<class T> inline T Max(T x,T y){return (x<y?y:x);}template<class T> T Abs(T a){return a>0?a:(-a);}template<class T> inline T lowbit(T n){return (n^(n-1))&n;}template<class T> inline int countbit(T n){return (n==0)?0:(1+countbit(n&(n-1)));}int ncase,ans,n,m[111],sum[111];double p[110],mxp,dp[11111];int main(){    scanf("%d",&ncase);    while(ncase--)    {        scanf("%lf%d",&mxp,&n);        sum[0]=0;        ff(i,1,n)        {            scanf("%d%lf",m+i,p+i);            sum[i]=sum[i-1]+m[i];        }       ff(i,1,sum[n]) dp[i]=111;        dp[0]=0.0;        ff(i,1,n)        {            ffd(j,sum[i-1],0)           checkmin(dp[j+m[i]],1-(1-dp[j])*(1-p[i]));        }        ans=0;        for(int i=1;i<=sum[n];++i)        if(dp[i]<=mxp) checkmax(ans,i);        printf("%d\n",ans);    }    return 0;}