Writing Bubble Sorting Function

Question

I'm trying to write a simple bubble sort function to sort some random data. Whenever executed though it simply prints the unsorted list as it was written initially. Where did i go wrong??? Code:

#include <cs50.h>
#include <stdio.h>

#define NUM_CITIES 10

typedef struct
{
    string city;
    int temp;
}
avg_temp;

avg_temp temps[NUM_CITIES] = {
    {"Austin", 97}, {"Boston", 82"}, {"Chicago", 85},
    {"Denver", 90}, {"Las Vegas", 105}, 
    {"Los Angeles", 82}, {"Miami", 97},
    {"New York", 85}, {"Phoenix", 107},
    {"San Fransisco", 66}
};

void sort_cities(void);

int main(void)
{
    sort_cities();

    printf("\nAverage July Temperatures by City\n\n");

    for (int i = 0; i < NUM_CITIES; i++)
    {
        printf("%s: %i\n", temps[i].city, temps[i].temp);
    }
}

void sort_cities(void)
{
    for (int i = 0; i < NUM_CITIES - 1; i++)
    {
        for (int j = 0; j < NUM_CITIES - i - 1; i++)
        {
            if (temps[j].temp < temps[j + 1].temp)
            {
                avg_temp initial = temps[j];
                temps[j] = temps[j + 1];
                temps[j + 1] = initial;
            }
        }
    }
}

I've tried thinking through things logically and step by step it makes sense to me, i do believe in the function it gets sorted but maybe not in my main somehow?

Answer 1

I had to change a couple of things so it would compile on godbolt, but mostly please see the changes I made to sort_cities() function. That was the pain point.

Note especially addition of variable need_sort.

LOGIC: As long as a swap is needed, the array still needs a sort. We always set need_sort = 0 (false) at the top of each loop. And if a swap is needed/performed, need_sort is set to 1 (true) again to flag that sorting must continue. On the last pass through the array, no swap is made because all the array components are in order, need_sort remains false, and the loop finally breaks.

In simple terms, this logic wasn't happening/executing in the original code. Hence sorting did not occur.

Also removed outer for() loop as while() improves and clarifies usage of variable need_sort.

Runnable code is provided here

#include <stdio.h>

#define NUM_CITIES 10

typedef struct
{
    char city[20];
    int temp;
}avg_temp;

avg_temp temps[NUM_CITIES] = {
"Austin",97,
"Boston",82,
"Chicago",85,
"Denver",90,
"Las Vegas",105,
"Los Angeles",82,
"Miami",97,
"New York",85,
"Phoenix",107,
"San Francisco",66
};


void sort_cities(void);

int main()
{
    
    sort_cities();

    printf("\nAverage July Temperatures by City\n");

    for (int i = 0; i < NUM_CITIES; i++)
    {
        printf("%s: %i\n", temps[i].city, temps[i].temp);
    }
    return 0;
}

void sort_cities(void)
{
int j, need_sort = 1;

    while(need_sort)
    {
        need_sort = 0;

        for (j = 0; j < NUM_CITIES-1; j++)
        {
            if (temps[j].temp > temps[j + 1].temp)
            {
                avg_temp initial = temps[j];
                temps[j] = temps[j + 1];
                temps[j + 1] = initial;
                need_sort=1;
            }
        }
    }
}

Output:

    
    Average July Temperatures by City
    San Francisco: 66
    Boston: 82
    Los Angeles: 82
    Chicago: 85
    New York: 85
    Denver: 90
    Austin: 97
    Miami: 97
    Las Vegas: 105
    Phoenix: 107

Answer 2

The logic for this is
for(i=0;i<n;i++)
{
    for(j=0;j<n-i-1;j++)
    {
       if([j]>array[j+1])
       {
         temp=array[j+1];
         array[j+1]=array[j];
         array[j]=temp;
       }
    }
}