Finding divisors of every number up to 100?

[Hayley777]

Hello,
I am trying to find the divisors of the numbers 2 through 100, add them up, and print them out as follows:
2: 1 = 1
3: 1 = 1
4: 1+2 = 3
5: 1 = 1
6: 1+2+3 = 6
...
100: 1+2+4+5....

I know how to find the divisors of one number, but I am having trouble iterating through all numbers up to 100 (I haven't even attempted the adding and printing yet). Right now I am just trying to get a list of all the divisors for numbers 1 through 100. All that prints when I run the program is a 1. Here is my code:

#include <iostream>
using std::cout;
using std::endl;
int main () {
int num = 2;
int i = 1;
while (num < 100)
{
if (num % i ==0 && i < num)
{
cout << i << endl;
i++;
}
if (i >= num)
{
i == 1;
num++;
}
else
{
i++;
}
}
return 0;
}

Thanks!!

[Mantorr22]

Is that how you sum up all factors for certain numbers?

#include <iostream>

using namespace std;

int main()
{
	int sum;
	bool bFirst;
	for(int i = 2; i <= 100; i++)
	{
		sum = 0;
		bFirst = false;
		std::cout << i << " : ";
		for(int j = 1; j < i; j++)
		{
			if(i % j == 0) // Is this number a factor?
			{
				sum += j;
				if(bFirst == false) bFirst = true; else std::cout << "+"; std::cout << j;
			}
		}
		std::cout << " = " << sum << std::endl;
	}
	
	return 0;
}

2 : 1 = 1
3 : 1 = 1
4 : 1+2 = 3
5 : 1 = 1
6 : 1+2+3 = 6
7 : 1 = 1
8 : 1+2+4 = 7
9 : 1+3 = 4
10 : 1+2+5 = 8
11 : 1 = 1
12 : 1+2+3+4+6 = 16
13 : 1 = 1
14 : 1+2+7 = 10
15 : 1+3+5 = 9
16 : 1+2+4+8 = 15
17 : 1 = 1
18 : 1+2+3+6+9 = 21
19 : 1 = 1
20 : 1+2+4+5+10 = 22
21 : 1+3+7 = 11
22 : 1+2+11 = 14
23 : 1 = 1
24 : 1+2+3+4+6+8+12 = 36
25 : 1+5 = 6
26 : 1+2+13 = 16
27 : 1+3+9 = 13
28 : 1+2+4+7+14 = 28
29 : 1 = 1
30 : 1+2+3+5+6+10+15 = 42
31 : 1 = 1
32 : 1+2+4+8+16 = 31
33 : 1+3+11 = 15
34 : 1+2+17 = 20
35 : 1+5+7 = 13
36 : 1+2+3+4+6+9+12+18 = 55
37 : 1 = 1
38 : 1+2+19 = 22
39 : 1+3+13 = 17
40 : 1+2+4+5+8+10+20 = 50
41 : 1 = 1
42 : 1+2+3+6+7+14+21 = 54
43 : 1 = 1
44 : 1+2+4+11+22 = 40
45 : 1+3+5+9+15 = 33
46 : 1+2+23 = 26
47 : 1 = 1
48 : 1+2+3+4+6+8+12+16+24 = 76
49 : 1+7 = 8
50 : 1+2+5+10+25 = 43
51 : 1+3+17 = 21
52 : 1+2+4+13+26 = 46
53 : 1 = 1
54 : 1+2+3+6+9+18+27 = 66
55 : 1+5+11 = 17
56 : 1+2+4+7+8+14+28 = 64
57 : 1+3+19 = 23
58 : 1+2+29 = 32
59 : 1 = 1
60 : 1+2+3+4+5+6+10+12+15+20+30 = 108
61 : 1 = 1
62 : 1+2+31 = 34
63 : 1+3+7+9+21 = 41
64 : 1+2+4+8+16+32 = 63
65 : 1+5+13 = 19
66 : 1+2+3+6+11+22+33 = 78
67 : 1 = 1
68 : 1+2+4+17+34 = 58
69 : 1+3+23 = 27
70 : 1+2+5+7+10+14+35 = 74
71 : 1 = 1
72 : 1+2+3+4+6+8+9+12+18+24+36 = 123
73 : 1 = 1
74 : 1+2+37 = 40
75 : 1+3+5+15+25 = 49
76 : 1+2+4+19+38 = 64
77 : 1+7+11 = 19
78 : 1+2+3+6+13+26+39 = 90
79 : 1 = 1
80 : 1+2+4+5+8+10+16+20+40 = 106
81 : 1+3+9+27 = 40
82 : 1+2+41 = 44
83 : 1 = 1
84 : 1+2+3+4+6+7+12+14+21+28+42 = 140
85 : 1+5+17 = 23
86 : 1+2+43 = 46
87 : 1+3+29 = 33
88 : 1+2+4+8+11+22+44 = 92
89 : 1 = 1
90 : 1+2+3+5+6+9+10+15+18+30+45 = 144
91 : 1+7+13 = 21
92 : 1+2+4+23+46 = 76
93 : 1+3+31 = 35
94 : 1+2+47 = 50
95 : 1+5+19 = 25
96 : 1+2+3+4+6+8+12+16+24+32+48 = 156
97 : 1 = 1
98 : 1+2+7+14+49 = 73
99 : 1+3+9+11+33 = 57
100 : 1+2+4+5+10+20+25+50 = 117

[Hengry]

Wouldn't the divisor also be the number itself? If the number is 50, the divisor would be 1, 2, 5, 10, 25 and also 50

[Hayley777]

Hengry, sorry I forgot to mention I'm doing all divisors excluding the number itself; otherwise you'd be right.

Thank you Mantor22!
Part of the issue was an == where there should have just been =. I used a sum variable but did it differently, since I don't really understand how to use bool. However, I'm stuck at how to not end each line of divisors with an extra '+'. Here is my code:

#include <iostream>
using std::cout;
using std::endl;
int main () {
        int num = 2;
        int i = 1;
        int sum = 0;
cout << num << ":";
while( num < 20 )
{       if (num % i == 0 && i < num)
        {sum = sum + i;
        cout << i << "+";
        i++;}
        else if (num % i != 0 && i < num)
       {i++;}
        else 
        {i = 1;
        num++;
        cout <<"=" << sum;
        cout << "\n" << num << ":";
        sum = 0;}
}
return 0;
}

Which gave me this result:
2:1+=1
3:1+=1
4:1+2+=3
5:1+=1
6:1+2+3+=6
7:1+=1
8:1+2+4+=7
9:1+3+=4
10:1+2+5+=8
11:1+=1
12:1+2+3+4+6+=16
13:1+=1
14:1+2+7+=10
15:1+3+5+=9
...