#include <iostream> #include <cstring> #include <cstdio> using namespace std; int test(string s) { string ss = ""; int flag = 0; for (int i = 0; i < s.size(); i++) { if (s[i] != '0') flag = 1; if (flag) ss += s[i]; } if (flag == 0) return 0; for (int i = 0; i < ss.size(); i++) if ((ss[i] != '4') and (ss[i] != '7')) return 0; int num = 0; for (int i = 0; i < ss.size() / 2; i++) num += ss[i] - '0'; int num1 = 0; int st = ss.size() / 2; if (ss.size() % 2 == 1) st++; for (int i = st; i < ss.size(); i++) num1 += ss[i] - '0'; if (num != num1) return 0; return 1; } int main() { int t; cin >> t; while (t--) { int n; cin >> n; string s; cin >> s; if (test(s)) cout << "YES" << endl; else cout << "NO" << endl; } return 0; }

#include<iostream> using namespace std; int main(){ int t,n,f,s1,s2; char c; cin>>t; while(t--){ cin>>n; s1=s2=0; f=1; for(int i=0;i<n;i++){ cin>>c; if(c-'0'!=4&&c-'0'!=7){ f=0; } if(i==n/2&&n%2){ continue; } if(i<n/2){ s1+=c; }else{ s2+=c; } } if(s1!=s2){ f=0; } cout<<(f?"YES\n":"NO\n"); } return 0; }

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