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  1. #include <iostream>
  2. #include <string>
  3. using namespace std;
  4.  
  5. int main() {
  6.     ios::sync_with_stdio(false);
  7.     cin.tie(nullptr);
  8.  
  9.     int t;
  10.     if (!(cin >> t)) return 0;
  11.     while (t--) {
  12.         int n;
  13.         string s;
  14.         cin >> n >> s;
  15.         int firstOne = -1;
  16.         int lastZero = -1;
  17.         for (int i = 0; i < n; ++i) {
  18.             if (s[i] == '1' && firstOne == -1) firstOne = i;
  19.             if (s[i] == '0') lastZero = i;
  20.         }
  21.         if (firstOne == -1 || lastZero == -1 || firstOne > lastZero) {
  22.             // no '1' before '0' => nothing to change
  23.             cout << s << '\n';
  24.         } else {
  25.             // print leading zeros
  26.             for (int i = 0; i < firstOne; ++i) cout << '0';
  27.             // the single '0' in the middle (ONLY one char)
  28.             cout << '0';
  29.             // print trailing ones
  30.             for (int i = lastZero + 1; i < n; ++i) cout << '1';
  31.             cout << '\n';
  32.         }
  33.     }
  34.     return 0;
  35. }
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/oZUpu4
language:
C++ (gcc 8.3)
created:
7 days ago
visibility:
public

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