Source of search_n2a.cpp


  1: //search_n2a.cpp

  3: #include <iostream>
  4: #include <vector>
  5: #include <algorithm>
  6: using namespace std;

  8: /**
  9: Tests if two positive integers have the same digit sum.
 10: Pre:\n i1 and i2 have been initialized and i1, i2 are both > 0.
 11: Post:\n Returns true if sum of the digits in i1 is == sum of digits
 12: in i2, and otherwise returns false.
 13: */
 14: bool digitSumsAreSame
 15: (
 16:     int i1, //in
 17:     int i2  //in
 18: )
 19: {
 20:     int digitSum1 = 0;
 21:     while (i1 != 0)
 22:     {
 23:         digitSum1 += i1 % 10;
 24:         i1 /= 10;
 25:     }

 27:     int digitSum2 = 0;
 28:     while (i2 != 0)
 29:     {
 30:         digitSum2 += i2 % 10;
 31:         i2 /= 10;
 32:     }
 33:     return digitSum1 == digitSum2;
 34: }

 36: int main()
 37: {
 38:     cout << "\nThis program illustrates the use of the STL search_n() "
 39:         "algorithm\n(extended version) to find instances of a consecutive "
 40:         "sequence of\nmatching values in a vector of integers, where "
 41:         "values match if and\nonly if they have the same digit sum.";
 42:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');

 44:     int a[] = {17, 27, 63, 54, 45, 71, 28, 81, 90, 18, 10, 9, 11};
 45:     vector<int> v(a, a+13);
 46:     cout << "\nHere are the contents of the vector:\n";
 47:     for (vector<int>::size_type i=0; i<v.size(); i++)
 48:         cout << v.at(i) << " ";
 49:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');

 51:     vector<int>::iterator p;

 53:     p = search_n(v.begin(), v.end(), 3, 9, digitSumsAreSame);
 54:     if (p != v.end())
 55:         cout << "\nThe first instance of three consecutive integers "
 56:             "\nwith a digit sum of 9 starts at location "
 57:             << (int)(p-v.begin()+1) << ".";
 58:     else
 59:         cout << "\nNo instance of three consecutive integers with a "
 60:             "\ndigit sum of 9 was found in the vector.";
 61:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');

 63:     p = search_n(p+1, v.end(), 3, 9, digitSumsAreSame);
 64:     if (p != v.end())
 65:         cout << "\nThe next instance of three consecutive integers "
 66:             "\nwith a digit sum of 9 starts at location "
 67:             << (int)(p-v.begin()+1) << ".";
 68:     else
 69:         cout << "\nNo further instance of three consecutive integers "
 70:             "\nwith a digit sum of 9 was found in the vector.";
 71:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');

 73:     p = search_n(p+1, v.end(), 3, 9, digitSumsAreSame);
 74:     if (p != v.end())
 75:         cout << "\nThe next instance of three consecutive integers "
 76:             "\nwith a digit sum of 9 starts at location "
 77:             << (int)(p-v.begin()+1) << ".";
 78:     else
 79:         cout << "\nNo further instance of three consecutive integers "
 80:             "\nwith a digit sum of 9 was found in the vector.";
 81:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');

 83:     p = search_n(p+1, v.end(), 3, 9, digitSumsAreSame);
 84:     if (p != v.end())
 85:         cout << "\nThe next instance of three consecutive integers "
 86:             "\nwith a digit sum of 9 starts at location "
 87:             << (int)(p-v.begin()+1) << ".";
 88:     else
 89:         cout << "\nNo further instance of three consecutive integers "
 90:             "\nwith a digit sum of 9 was found in the vector.";
 91:     cout << "\nPress Enter to continue ... ";  cin.ignore(80, '\n');
 92: }