I am currently learning C++. I run into troubles when I work on an Overloading problem. The function in the class supposed to receive the array and size of the array as input and output the smallest value. There are three arrays in total including int, float, and char. My code works only under int. I can't understand why I have attached my code below. Can anyone tell my mistake?
I know there must be a better method than mine, I really wanna to figure out why my code doesn't work for float and char case. Any help will be greatly appreicated.

For the int case, it can correctly output the smallest value which is 2. However for the float condition, it keeps giving me 0 instead a number from the float list.

Main function

int main()

{

  Compare c;

  int arrayInt[5] = {65,43,2,898,678};

  float arrayInF[4] = {4.5,4.9,4.3,6.5};

  char arrayInC[6] = {'w','z','t','h','e','c'};



  std::cout<<c.findSmaller(arrayInt, 5)<<" is the smallest of the input arrayn";

  std::cout<<c.findSmaller(arrayInF, 4)<<" is the smallest of the input arrayn";

  std::cout<<c.findSmaller(arrayInC, 6)<<" is the smallest of the input arrayn";

  return 0;

}

Class

class Compare

{

public:

    int findSmaller(int input1,int input2);

    float findSmaller(float input1,int input2);

};





int Compare::findSmaller(int input1, int input2)

{

int small;

for(int i=0;i<input2;i++)

{

    if(input1[i]<input1[i+1])

    {

        small = input1[i];

        input1[i+1] = small;

    }

    else

    {

        small = input1[i+1];

        input1[i+1] = small;

    }

}

return small;

}



float Compare::findSmaller(float input1, int input2)

{

float small;

for(int i=0;i<input2;i++)

{

    if(input1[i]<input1[i+1])

    {

        small = input1[i];

        input1[i+1] = small;

    }

    else

    {

        small = input1[i+1];

        input1[i+1] = small;

    }

}

return small;

}



char Compare::findSmaller(char input1, int input2)

{

char small;

for(int i=0;i<input2;i++)

{

   if(input1[i]<input1[i+1])

{

    small = input1[i];

    input1[i+1] = small;

}

else

{

    small = input1[i+1];

    input1[i+1] = small;

}

}

return small;

} 

The reason the code does not work as you expect is two fold

1. because your algorithm is destructive


2. because you are overstepping array bounds

your code snippet:

if(input1[i]<input1[i+1]) // <-- 2) over step array when i = (input2 - 1)

{

    small = input1[i];

    input1[i+1] = small;  // <-- 1) this will overwrite the NEXT value

}

else

{

    small = input1[i+1];

    input1[i+1] = small;

}

if you walk through this with your arrayInt input

int arrayInt[5] = {65,43,2,898,678};

the data becomes {65, 43, 2, 2, 2} as it executes, destroying the original data.

c and c++ use 0 base indexing, meaning a 4 element array is indexed 0, 1, 2, 3, etc so when you are iterating "i < input2" where input2 = 5 the first iteration i will equal 0 and the last iteration i will equal 4. When your code then makes reference to input1[i+1] that would then be input1[5] which is out of bounds but not necessarily undefined nor 0. You see, the compiler will try to allocate an array in a continuous block of memory like so:

| item 0 | item 1 | item 2 | item 3 | item 4 | etc.

referencing input1[5] will simply return the next block of memory interpreted as the expected data type, an integer in the case of arrayInt.

Since the 3 arrays are declared together, the compiler allocated their space together, this means that arrayInt is adjacent to arrayInf in physical memory, which also means that arrayInt[5] would be the same as (int)arrayInf[0]. 4.5 float is a large integer and will engage the destructive nature of your algorithm, meaning that when iterating over the arrayInt you actually overwrote the 4.5 float with an integer 2 and that's going to be interpreted as a really small float, so you've clobbered the first element of the arrayInf array.

@Bo-r gives an example of a better algorithm for doing what you want.

float arrayInF[4] = {4.5, 4.9, 4.3, 6.5};

has 4 values (use whitespace in your code, it makes reading it much easier)

You pass in an input2 (use more descriptive variable names, too) of 4 which means that

for(int i=0;i<input2;i++)

i goes up to 3.

You then access array indices 3 and 3+1=4 here (and other places as well):

if(input1[i]<input1[i+1])

When you only have valid indices up to 3, which completely breaks your program. Once you read/write invalid memory locations, the behavior of your program becomes undefined. It may still look like it's working sometimes, but that's just sheer luck.

This problem is not limited to just the float implementation.

Seems you haven't declare and implemented the method char Compare::findSmaller(char *input1, int input2).

A example of such an implementation would be:

char Compare::findSmaller(char input1, int input2) {

    assert(input2 >0);

    char small = input1[0];

    for (int i = 1; i < input2; i++)

        if (input1[i] < small)

            small = input1[i];

    return small;

}