Why this program to sort array doesnt work?

Question

Im trying to learn C and I'm doing this program to sort an array but It doesn't work and I'm not sure why, I tested each function and works well, someone knows if its a problem of variables or something?

#include <stdio.h>
#include <stdlib.h>

#define N 5

int V[5] = { -383, 386, 277, 415, 293 };

void displayArray(int arr[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        printf("%d ", arr[i]);
}

int maxim(int v[], int n)
{
    int i, m;
    m = v[0];
    /*
    Find maxim element
    */
    for (i = 1; i < n; i++)
        if (v[i] > m)
            m = v[i];
    /*
    Search element position
    */
    for (i = 0; i < N; i++)
        if (v[i] == m)
            return i;
}

void sort(int v[], int n)
{
    int i, pos, t;
    for (i = 0; i < n; i++)
        pos = maxim(v, n - i);

        /*
        Swap elements
        */
        t = v[n - 1 - i];
        v[n - 1 - i] = v[pos];
        v[pos] = t;
}

int main()
{
    displayArray(V, N);
    sort(V, N);
    printf("\n");
    displayArray(V, N);
    return 0;
}

The output is

-383 386 277 415 293 - Original Array

21900 386 277 415 293 - 'Sorted' Array

Answer 1

First fix your maxim function. Its purpose is to find the maximum index of a sequence v of magnitude n . Therefore, remembering the maximum value in m is irrelevant; you want to remember where it resides :

int maxim(int v[], int n)
{
    int m=0;
    for (int i=1; i<n; ++i)
    {
        if (v[m] < v[i])
            m = i; // save new max location
    }
    return m;
}

After that, the sort, which is completely wrong. This:

int i, pos, t;
for (i = 0; i < n; i++)
    pos = maxim(v, n - i);

is pointless. It calculates, and overwrites, pos repeatedly until the last iteration, which is the only one that is processed with:

t = v[n - 1 - i];
v[n - 1 - i] = v[pos];
v[pos] = t;

E..g, you sort one element, and then exit your sort. You need to sort them all , starting with the full segment, then reducing the size of the segment by one with each iteration after you swap the most-maximum element into position for that segment.

void sort(int v[], int n)
{
    for (int i=0; i<(n-1); ++i)
    {
        int m = maxim(v, (n-i)); // max of this segment
        int tmp = v[m];
        v[m] = v[n-i-1];
        v[n-i-1] = tmp;
    }
}

Answer 2

pos = maxim(v, n - i);

should be

pos = maxim(v, n);

Answer 3

Your program is inefficient, but almost correct. The only place where you must focus is:

void sort(int v[], int n)
{
    int i, pos, t;
    for (i = 0; i < n; i++)
        pos = maxim(v, n - i);

        /*
        Swap elements
        */
        t = v[n - 1 - i];
        v[n - 1 - i] = v[pos];
        v[pos] = t;
}

Well, C is not Python, so if, after getting pos you want to swap the elements of your array, then you need to group all of the for loop in braces, as in:

void sort(int v[], int n)
{
    int i, pos, t;
    for (i = 0; i < n; i++) {
        pos = maxim(v, n - i);

        /*
        Swap elements
        */
        t = v[n - 1 - i];
        v[n - 1 - i] = v[pos];
        v[pos] = t;
    }
}