1: //set_symmetric_difference2a.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 "
39: "set_intersection() algorithm\n(extended version) to find the "
40: "values that are in a first vector of integers\nbut not in a "
41: "second vector of integers, as well as those integers that are "
42: "\nin the second vector but not in the first, and write them out "
43: "to a third\nvector of integers. In this case the vectors are "
44: "ordered in the sense that\none integer comes before another "
45: "if and only if it has a smaller digit sum.";
46: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
48: int a1[] = {11, 12, 12, 12, 12, 13, 14, 15};
49: vector<int> v1(a1, a1+8);
51: cout << "\nHere are the values in the vector v1:\n";
52: for (vector<int>::size_type i=0; i<v1.size(); i++)
53: cout << v1.at(i) << " ";
54: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
56: int a2[] = {2, 21, 21, 31, 31, 61, 71, 81};
57: vector<int> v2(a2, a2+8);
59: cout << "\nHere are the values in the vector v2:\n";
60: for (vector<int>::size_type i=0; i<v2.size(); i++)
61: cout << v2.at(i) << " ";
62: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
64: int a3[] = {101, 102, 103, 104, 105, 106, 107, 108, 109, 110,
65: 111, 112, 113, 114, 115};
66: vector<int> v3(a3, a3+15);
68: cout << "\nHere are the values in the vector v3:\n";
69: for (vector<int>::size_type i=0; i<v3.size(); i++)
70: cout << v3.at(i) << " ";
71: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
73: cout << "\nNow we find the values that are in v1 but not in v2, "
74: "as well as those that are\nin v2 but not in v1, and write "
75: "them out to v3, starting at the beginning of v3.";
76: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
78: vector<int>::iterator p;
79: p = set_symmetric_difference(v1.begin(), v1.end(),
80: v2.begin(), v2.end(), v3.begin(), hasSmallerDigitSum);
82: cout << "\nHere are the revised contents of v3:\n";
83: for (vector<int>::size_type i=0; i<v3.size(); i++)
84: cout << v3.at(i) << " ";
85: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
87: cout << "\nThe iterator returned by the algorithm is pointing at "
88: "the value " << *p << ".";
89: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
90: }