第三题这样子正确吗 #include<iostream> #include<vector> #include<algorithm> using namespace std; int ispalindrome(vector<int> &a); int main() {     int n;     cin>>n;     int i=0;     int sum=0;     for(i=0;i<=n;i++)     {         vector<int> vv;         int t=i;         int s=0;         if(i==0)             sum=sum+1;         else         {             while(t)             {                 s=t%2;                 vv.push_back(s);                 t=t/2;                         }             sum=sum+ispalindrome(vv);         }             }     cout<<sum<<endl;     return 0; } int ispalindrome(vector<int> &a) {     int i=0,j=a.size()-1;     for(i=0,j=a.size()-1;i<j;i++,j--)     {         if(a[i]!=a[j])             return 0;     }     return 1; }