While Loop in For Loop - c++

Question

I'm trying to count the cats and dogs in a string. So,
for example:
if the string is "cc+dd-cd",:
I want to count 2 positive cats, 2 positive dogs, 1 negative cat, 1 negative dog (yes I know this is a weird way to count, but it's part of my assignment).
I thought about doing a for loop where I iterated over the string, then nested inside the for loop, I'd have a while loop that would run until a '-', then run until a '+' or the end. I started the code, and without even getting that far into it, it created an infinite loop.
Question: How can I fix it?
Thanks!
string animalparkString = "cc+dd-cd"
for (int k = 0; k != animalparkString.size(); k++)
{
while (k != '-'){
pdc = pdc + 1; //positive dog count
pcc = pcc + 1; //positive cat count
}
while (k != '+') {
ndc = ndc + 1;
ncc = ncc + 1;
}
}

Answer 1

The immediate issue is that the while loops check k's value, but don't modify it. So once you entered one of them you'll be stuck there infinitely as k doesn't change inside the loop's body.
I wouldn't bother with nested loops - I'd just go over the entire string in one loop, and evaluate each character in its turn. A neat way to accomplish this is to keep a state of whether you're adding or subtracting (according to whether you last encountered a + or a - sign:
bool positive = true;
string animalparkString = "cc+dd-cd";
for (int k = 0; k < animalparkString.size(); k++) {
char ch = animalparkString[k];
switch (ch) {
case '+':
positive = true;
break;
case '-':
positive = false;
break;
case 'c':
if (positive) {
pcc++;
} else {
ncc++
}
break;
case 'd':
if (positive) {
pdc++;
} else {
ndc++
}
break;
}
}

Answer 2

This post describes iterating all characters is a string.
This is a simple solution using modern C++:
int sign = 1;
int dogs_count = 0, cats_count = 0;
std::string animalparkString = "-cccccc+dddd-cd";
for (const char& ch : animalparkString)
{
switch (ch) {
case '+':
sign = 1;
continue;
case '-':
sign = -1;
continue;
case 'c':
cats_count += sign;
continue;
case 'd':
dogs_count += sign;
continue;
}
}
std::cout <<"dogs: " << dogs_count << " cats: " <<cats_count;
A couple of suggestions to help you get started:
1. Use online c++ compilers to quickly test code
2. If your code doesn't behave as expected, use step-by-step debugging in your IDE or print our variables as you go using std::cout
3. Explicitly stating namespace is considered good practice. i.e:
// preferable:
std::string myString;
// avoid:
using namespace std;
string myString

Answer 3

To make your code work without too many changes , you can simply replace the while() condition with an if(). Moreover, instead of checking the iterator value k, you should compare the kth string element animalparkString[k].
Then you might start wondering if the code you wrote is actually doing what you expect. Possible questions you could try to answer is "how do I distinguish between positive or negative counts" and, then, "how do I distinguish between cats and dogs "? You will probably need to check also for cs and ds, not only for the operation sign!
string animalparkString = "cc+dd-cd"
for (int k = 0; k != animalparkString.size(); k++)
{
if(animalparkStrink[k] != '-'){
// Now you know, there will be a pos count. Dog or Cat?
}
if(animalparkString[k] != '+') {
// Now you know, there will be a neg count. Dog or Cat?
}
}
Note that if you write while( k != '-'), it will always evaluate true and, therefore, you will be stuck there. If it is the first time working with for-loops, consider printing the iterator value, to understand when and where you are stuck.
string animalparkString = "cc+dd-cd"
for (int k = 0; k != animalparkString.size(); k++)
{
std::cout << "for-loop iteration number: " << k << std::endl;
if(animalparkStrink[k] != '-'){
// Now you know, there will be a pos count. Dog or Cat?
}
if(animalparkString[k] != '+') {
// Now you know, there will be a neg count. Dog or Cat?
}
}

Answer 4

for and while together approach is unnecessarily complicated. Here's a simpler solution:
#include <concepts>
#include <iostream>
int main() {
auto const& str{"cc+dd-cd"};
std::boolean auto isPositive = 1;
std::integral auto pdc{0}, pcc{0}, ndc{0}, ncc{0};
for (char const ch : str) {
switch (ch) {
case 'c': {
pcc += isPositive;
ncc += !isPositive;
break;
}
case 'd': {
pdc += isPositive;
ndc += !isPositive;
break;
}
case '+': {
isPositive = true;
break;
}
case '-': {
isPositive = false;
break;
}
}
}
std::cout << "pcc: " << pcc << '\n'
<< "ncc: " << ncc << '\n'
<< "pdc: " << pdc << '\n'
<< "ndc: " << ndc << '\n';
}
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