Find char* element in array of char* in C++

Question

I'm trying to write function that search for char * element in array of char* and the function start check this element, if the element exist in the array I will have "found", if not it should be "inserted" and the element added to the array.

I wrote this code but I cannot know how to try it, the program always gives me exception, what can I do to check the element in my pointer array?

void checkFunction(char*myArray[], char *element,bool flag)
{
    for (int i = 0; i < strlen(*myArray) ; ++i)
    {
        if (myArray[i] == element)
        {
            flag = true;
        }
    }
    *myArray = element;
    flag = false;

    if (flag)
    {
        cout << "Found" << endl;
    }
    else
    {
        cout << "Inserted" << endl;
    }
}

You aren't ready to use poiners and arrays, which are advanced low-level language features for experts. Please use std::string and std::vector. — Kerrek SB
– Kerrek SB, Commented Dec 20, 2015 at 23:45
When you compare a char pointer with another char pointer, you're not comparing their values. You're comparing their positions on memory. You have to check them like that: strcmp(a, b) == 0; — Paulo
– Paulo, Commented Dec 20, 2015 at 23:46

Marko Tunjic · Accepted Answer · 2015-12-21 00:16:03Z

2

C++ Way

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(int argc, const char * argv[]) {

    vector<string> myStrings { "One", "Two", "Three" };

    // std::find()  finds the first element that matches a value
    auto it = find(begin(myStrings), end(myStrings),  "Twooo");
    if (it != end(myStrings)) {
        cout << "We found this string; do something..." << endl;

    }


}

answered Dec 21, 2015 at 0:16

Marko Tunjic

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Comments

Ziezi · Accepted Answer · 2015-12-21 00:36:08Z

0

Few remarks regarding your function:

1.Why do you need the third parameter bool flag, instead of having it as local variable?

2.If you want to expand an array you should copy the old to a newly allocated and then add the new element, you can not just do: *myArray = element;

3.If you want to iterate through the array length/ size, instead of:

for (int i = 0; i < strlen(*myArray) ; ++i)

pass an additional parameter to your function, that indicates the number of elements in the array.

With std::string and std::vector you could do something like:

void check_insert (std::vector<std::string>& v, std::string& c) {

    for (auto i = 0; i < v.size(); ++i) {
        if (v[i] == c) {
            std::cout << "Found!\n";
            return;
        }
    }

    v.push_back(c);
    std::cout << "Inserted!\n";
}

edited Dec 21, 2015 at 0:36

answered Dec 20, 2015 at 23:59

Ziezi

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3 Comments

Keith Over a year ago

Mostly good. But I think your for loop with arr_begin, arr_end is wrong. Each of those is a pointer to a char* anywhere in memory, not the location of the array elements themselves. itself. for(auto i = myArray; i != &myArray[n];++i)

Ziezi Over a year ago

@Keith a pointer to the first element of an array, when incremented n times, where n = array-size will 100% reach the last element, as "an array is a homogeneous sequence of objects allocated in contiguous memory."

Keith Over a year ago

Yes, exactly. However, your now deleted code was setting arr_begin to the value contained in first element, not the address of the first element.

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