ACdream1726A Math game

Recently, Losanto find an interesting Math game. The rule is simple: Tell you a number H, and you can choose some numbers from a set {a[1],a[2],……,a[n]}.If the sum of the number you choose is H, then you win. Losanto just want to know whether he can win the game.
Input
There are several cases.
In each case, there are two numbers in the first line n (the size of the set) and H. The second line has n numbers {a[1],a[2],……,a[n]}. 0

//4ms 1084k#include<stdio.h>#include<string.h>long long a[50],sum[50];int flag,n,h;void dfs(long long cnt,int m)//cnt是当前累加的和,m是当前累加了几个数 {    if(cnt==h) {flag=1;return;}    if(flag||m==n+1) return;    if(sum[n]-sum[m-1]+cnt<h||cnt>h) return;    dfs(cnt+a[m],m+1);    dfs(cnt,m+1);    return;}int main(){    while(~scanf("%d%lld",&n,&h))    {        memset(sum,0,sizeof(sum));        flag=0;        for(int i=1;i<=n;i++)        {            scanf("%lld",&a[i]);            sum[i]=sum[i-1]+a[i];        }        dfs(0,1);        if(flag) printf("Yes\n");        else printf("No\n");    }    return 0;}

//4ms 1084k#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;int n,m,a[45],sum[45];int dfs(int top,int s){    if(s==m) return 1;    if(top>=n||s>m||sum[n]-sum[top]+s<m) return 0;    if(dfs(top+1,s)) return 1;    if(dfs(top+1,s+a[top])) return 1;    return 0;}int main(){    while(~scanf("%d%d",&n,&m))    {        sum[0]=0;        for(int i=0;i<n;i++)        {            scanf("%d",&a[i]);            sum[i+1]=sum[i]+a[i];        }        if(sum[n]<m) printf("No\n");        else if(dfs(0,0)) printf("Yes\n");        else printf("No\n");    }    return 0;}

//988ms 1084k#include<stdio.h>#include<string.h>#include<algorithm>using namespace std;int n,m,a[45],sum[45],book[45];int dfs(int top,int s){    if(top>=n||s>m) return 0;    if(s==m) return 1;    for(int i=top;i<n;i++)    {        if(book[i]||sum[n]-sum[i]+s<m) continue;        book[i]=1;        if(dfs(top+1,s+a[i])) return 1;        book[i]=0;    }    return 0;}int main(){    while(~scanf("%d%d",&n,&m))    {        memset(book,0,sizeof(book));        sum[0]=0;        for(int i=0;i<n;i++)        {            scanf("%d",&a[i]);            sum[i+1]=sum[i]+a[i];        }        if(sum[n]<m) printf("No\n");        else if(dfs(0,0)) printf("Yes\n");        else printf("No\n");    }    return 0;}