1: //max2a.cpp
3: #include <iostream>
4: #include <vector>
5: #include <algorithm>
6: using namespace std;
8: /**
9: Tests if one integer has a smaller digit sum than another.
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 hasSmallerDigitSum
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 max() "
39: "algorithm (extended version)\nto find the maximum of two "
40: "integer literal values, the maximum of two integer\nvalues "
41: "stored in simple integer variables, and (in two different "
42: "ways) the\nmaximum of two integer values stored in a vector "
43: "of integers. In this case,\none integer is larger than "
44: "another if and only if it has a greater digit sum.";
45: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
47: cout << "\nFirst, we find the maximum of two integer "
48: "literal values.\n";
49: cout << "max(16, 23) = " << max(16, 23, hasSmallerDigitSum);
50: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
52: int first = 7;
53: int second = 10;
54: cout << "\nNext, we find the maximum of two integer "
55: "\nvalues stored in simple integer variables.";
56: cout << "\nfirst = " << first << " second = " << second << endl;
57: cout << "max(first, second) = "
58: << max(first, second, hasSmallerDigitSum);
59: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
61: int a[] = {39, 66, 110, 81, 47};
62: vector<int> v(a, a+5);
64: cout << "\nHere are the integer values in the vector:\n";
65: for (vector<int>::size_type i=0; i<v.size(); i++)
66: cout << v.at(i) << " ";
67: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
69: cout << "\nNow we find the maximum of the first and last values "
70: "\nstored in the vector of integers using one approach.";
71: cout << "\nmax(v.at(0), v.at(4)) = "
72: << max(v.at(0), v.at(4), hasSmallerDigitSum);
73: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
75: cout << "\nFinally, we find the maximum of the first and last values "
76: "\nstored in the vector of integers using a second approach.";
77: cout << "\nmax(*v.begin(), *(v.end()-1)) = "
78: << max(*v.begin(), *(v.end()-1), hasSmallerDigitSum);
79: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
80: }