Help Me! Why is this stopping ?

Question

I recently was trying to create a solver for Agus Mei's Quiz No. 3, 100.
So, I created this:

#include<bits/stdc++.h>
using namespace std;
bool nozero(int no)
{
int d;
while(no!=0)
{
d=no%10;
if(d==0)
return false;
no/=10;
}
return true;
}
void f()
{
int x,y,z,a;
for(int i=0;i<1000;i++)
{
x=1+(rand()%98);
if(nozero(x))
break;
else
continue;
}
a=100-x;
for(int i=0;i<1000;i++)
{
for(int j=0;j<100;j++)
{
y=rand();
if(nozero(y))
break;
else
continue;
}
for(int k=0;k<100;k++)
{
z=rand();
if(nozero(z))
break;
else
continue;
}
if((y/z==a&&y%z==0))
break;
else
continue;
}
cout<<x<<"+"<<y<<"/"<<z<<endl;
}
int main(void)
{
srand(time(0));
for(int i=0;i<5;i++)
f();
}

But on running, it on my PC, I encounter the following problem, that it sometimes stop working, and prints only few of the correct answers. (Sometimes all, sometimes none.)

So, how to repair the program?

I guess I should make the program save the results in a file, so that whenever it works, the correct ones are saved. This will help me get many results // Atleast after 10-15 runs...

Edit : Now, even the answers are coming wrong. Why?

Answer 1

1.
Your code crashes because you attempt to divide by 0.

z = rand() can return 0, then your nozero function simply returns true so further down the line y / z will cause a divide by 0.

2.
You're not checking if the digits in the equation are unique, unless you don't want to of course :P

If checking for uniqueness then using rand will take forever to get even 1 answer, unless you're extremely lucky.

3.
After 1000 attempts your for loop quits and outputs its last data, thats why they are all wrong

Here is my implementation in C++, this does not work on the playground because std::to_string is bugged.
(works on code blocks at least)

#include <iostream>
#include <cmath>
#include <vector>

bool areUnique(std::string n)
{
int arr[] = {0,1,1,1,1,1,1,1,1,1};

for(const auto &i: n)
{
if(isdigit(i))
{
if(arr[i - '0'])
--arr[i - '0'];
else
return false;
}
}

//Also check if all digits are used, except 0
for(int i = 1; i < 10; ++i)
if(arr[i])
return false;

return true;
}

std::vector<int> getDivisors(int n)
{
std::vector<int> divisors;
int sq = sqrt(n);
for(int i = 1; i <= sq; ++i)
{
if(n % i == 0)
{
divisors.push_back(i);
divisors.push_back(n / i);
}
}

return divisors;
}

int main()
{
const int TARGET = 100;

for(int y = 1; y < 100000; ++y)
{
for(const auto& z: getDivisors(y))
{
int x = TARGET - y / z;

if(x > 0)
{
if(areUnique(std::to_string(x) + std::to_string(y) + std::to_string(z)))
{
std::cout << x << " + " << y << " / " << z << std::endl;
}
}
}
}
}

Answer 2

After some observation, I was able to see that y/z is never returning to be == a, perhaps because the loop ends by that time.

I'll now try using an infinite loop, which will be slower, but may return an answer...

Edit :

That didn't work. Not at all. No answer at all. ;..(

Answer 3

@Dennis
1) I was Stupid to not make an if for the no==0...
2) I assumed rand() which would be run 1000 times may return me unique data, but I forgot that it is a pseudo-random generator. - I'll redesign it with a randon_distribution_engine...

Thanks a lot! You're Great!...

Answer 4

Trying it, but unable to find any problem...

Answer 5

These are some run results...

6+13673/29839
21+23174/5618
76+23666/7759
51+26978/32728
47+15818/19776
74+21382/3245
47+21439/558
32+6359/13973
3+28541/1724
57+3669/25733
18+5681/6152
59+28338/9311
81+21829/1858
25+26926/23925
61+31658/4694
94+17418/17871
87+31395/22289
64+17493/25448

Why are 'all' of them wrong?

Answer 6

have you tried debugging it?