CODEWITHSUNDEEP
carraysfile
user3298129
user3298129

Reputation: 59

Finding the sum of elements of the largest sub array of increasing order in C?

I have a file named sample.txt which contains 1000 integers(both positive and negative numbers). First I copied the file into an array of size 1000 (say a). My aim is to locate the largest sub array in a and find the sum of elements in it. An array is a sub array if it's consecutive elements are in increasing order. For example in the array {12,23,3,1,-56,2,4,6,45,49,1,2,-10} the sub array is {-56,2,4,6,45,49}. Then I need to calculate the sum of elements of this sub array.

Given below is my attempt to solve the problem using a C program. I'm a non-CS major just finished C programming in this semester. Your help would be very much appreciated.

int sum(int a[],int i,int temp)
{
 int sum=0,j;
 for(j=i;j<i+temp;j++)
  sum+=a[j];
 printf("Sum = %d", sum); 
 return 0;
}

int main()
{
    FILE *f1;
    int a[1000],b[900];
    int number,i=-1,counter=0,temp=1,check=1,j;
    f1 = fopen("sample.txt","r");
    while (!feof (f1) && fscanf (f1, "%d", &number) && i++ < 1000 )// copying the file to an array
    a[i] = number;
    fclose(f1);
    for(i=1;i<1000;i++)
    {
     if(a[i-1]<a[i])
      counter++;
     else
     {
       if(counter>temp)
         temp=counter;
       counter=0;
      } 
    }
    temp++;
    printf("Temp= %d", temp); // the length of the largest sub array whose elements are in increasing order
    sum(a,i,temp);      
    return 0;
}

Upvotes: 0

Views: 465

Answers (4)

Lee Duhem
Lee Duhem

Reputation: 15121

to locate the largest sub array in a

"To locate the largest", I suppose you mean longest sub-array.

Anyway, here is an implementation (it works for your test input):

int longest_increasing(int array[], int length, int *start, int *end)
{
    int pos, curr_pos;

    *start = 1;
    *end = 0;

    curr_pos = 0;
    while (curr_pos + 1 < length) {
        while (curr_pos+1 < length && array[curr_pos] >= array[curr_pos+1])
            curr_pos++;

        for (pos = curr_pos; pos+1 < length && array[pos] < array[pos+1]; pos++)
            ;

        if (*end - *start < pos - curr_pos) {
            *start = curr_pos;
            *end = pos;
        }
        curr_pos = pos+1;
    }

    if (*start < *end)
        return 1;
    else
        return 0;
}

Upvotes: 0

Joe
Joe

Reputation: 1432

I introduced a new variable temp_index which will hold the starting index of the largest sub-array and used j to store the starting index in the loop.

Try this

 if(a[i-1]<a[i])
 { 
  if (counter == 0) { j = i }
  counter++;
 }
 else
 {
   if(counter>temp) {
     temp_index = j;
     temp=counter;
   }
   counter=0;
  } 
}
temp++;
printf("Temp= %d", temp); // the length of the largest sub array whose elements are in increasing order
sum(a,temp_index,temp)

Upvotes: 0

Daniel Bejan
Daniel Bejan

Reputation: 1468

Well, I come from C++ but maybe I can help..you could try this : 

for(i=1;i<=1000;i++)
    {
     if(a[i]<a[i+1])
      counter++;

Upvotes: 0

barak manos
barak manos

Reputation: 30136

Just a general advice, in order to prevent your program from crashing:

Change this:

while (!feof (f1) && fscanf (f1, "%d", &number) && i++ < 1000 )
    a[i] = number;

To this:

while (!feof (f1) && fscanf (f1, "%d", &number) && i < 1000 )
    a[i++] = number;

Upvotes: 1

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