这是第三题，来帮我改改呀~~

include

using namespace std; int f(int a[],int n,int m,int s,int l) { if(a[m]+l==s){return 1+f(a,n,m+1,s,l);} if(n!=m){return f(a,n,m+1,s,l+a[m])+f(a,n,m+1,s,l);} else{return 0;} } int main() { int n,s; cin>>n>>s; n--; int a[n]; for(int i=0;i>a[i]; } cout<<f(a,n,0,s,0); return 0; }

qwq嘤嘤嘤窝怎么改都改不好惹o(╥﹏╥)o，有没有大佬帮人家看看呀(๑•̀ㅂ•́)و✧，蟹蟹(･ω･)ﾉ！ 这是第二题二分搜索

include

using namespace std; int half(int a[],int n,int s,int k) { int low=s,high=n; int mid=high/2; if(k>a[mid]){return half(a,high,mid,k);} if(k<a[mid]){return half(a,mid,low,k);} if(k=a[low]){return low;} if(k=a[high]){return high;} if(low+1==high&&low==high){return -1;} }

int main() { int n,k; cin>>n; int a[n]; for(int i=0;i>a[i]; } cin>>k; int ans=half(a,n-1,0,k); if(ans!=-1){ans++;} cout<<ans; return 0; }