sort array of integers lexicographically C++

Question

I want to sort a large array of integers (say 1 millon elements) lexicographically.

Example:

input [] = { 100, 21 , 22 , 99 , 1  , 927 }
sorted[] = { 1           


        

Answer 1

Overload the < operator to compare two integers lexicographically. For each integer, find the smallest 10^k, which is not less than the given integer. Than compare the digits one by one.

class CmpIntLex {
int up_10pow(int n) {
  int ans = 1;
  while (ans < n) ans *= 10;
  return ans;
}
public: 
bool operator ()(int v1, int v2) {
   int ceil1 = up_10pow(v1), ceil2 = up_10pow(v2);
   while ( ceil1 != 0 && ceil2 != 0) {
      if (v1 / ceil1  < v2 / ceil2) return true;
      else if (v1 / ceil1 > v2 / ceil2) return false;
      ceil1 /= 10; 
      ceil2 /= 10;
   }
   if (v1 < v2) return true;
   return false;
}
int main() {
vector vi = {12,45,12134,85};
sort(vi.begin(), vi.end(), CmpIntLex());
}