C program - find largest sequence in array

Question

Given this example :

int arr[3][7] = {       {1,0,0,1,1,1,1},  //should output 4
                        {0,1,1,1,1,0,1},  //should output 4
                        {0,0,1,1,1,1,1}}; //should output 5

Find the largest sequence containing number 1, and print line index and number of 1.

Do not count total numbers of 1 in each line. Only if they are one after another.

here is my approach :

int main(){
    int i,j,c=0,count=0;

    int arr[3][7] = {   {1,0,0,1,1,1,1},  //output 4
                        {0,1,1,1,1,0,1},  //output 4
                        {0,0,1,1,1,1,1}}; // output 5

    for(i=0; i<3; i++){
        for(j=0; j<7; j++){
            if(arr[i][j] == 1){
                c++;
            } else if( arr[i][j] == 0 && c > count ) {
                count = c;
                c = 0;
            }
        }
        printf("%d\n", count);
    }

  return 0;
}

What i want to get as output now is 4,4,5 but i am getting 1,4,5.

SOLUTION thanks to https://stackoverflow.com/users/1228887/twain249

int main(){
    int i,j,c=0,count=0;

    int arr[3][7] = {   {1,1,0,1,1,1,1},  //output 4
                        {0,1,1,1,1,0,1},  //output 4
                        {0,0,1,1,1,1,1}}; // output 5

    for(i=0; i<3; i++){
        for(j=0; j<7; j++){
            if(arr[i][j] == 1){
                c++;
            } else {
                count = c;
                c = 0;
            }
        }
        if(c > count){
            count = c;
        }
        printf("%d\n", count);
        c=0;
    }
    return 0;
}

Learn how to debug your small programs ericlippert.com/2014/03/05/how-to-debug-small-programs — zerkms
– zerkms, Commented Feb 25, 2018 at 23:32
@zerkms i am beginner in C language and do not know how to write test functions properly. — trying to learn
– trying to learn, Commented Feb 25, 2018 at 23:38
The article also mentions a debugger. If you tried to debug your code you'd spot the problem instantly. — zerkms
– zerkms, Commented Feb 25, 2018 at 23:45
Your solution fails case like this { 1,1,1,0,1,1,0 } returns 2 instead of 3 — Killzone Kid
– Killzone Kid, Commented Feb 25, 2018 at 23:51

twain249 · Accepted Answer · 2018-02-25 23:39:57Z

1

You forgot to handle the case where the longest sequence is the end of the list

after the inner j loop add the following

if (c > count) {
    count = c;
}

Also you forgot to add a clear after each check.

After the printout add

c = clear = 0;

EDIT: 1 more error. You need to reset c even if the new sequence isn't the longest.

Change the else if into

else if (arr[i][j] == 0) { // If isn't necessary if 0/1 are your only options
{
    if (c > count) {
        count = c;
    }
    c = 0;
}

edited Feb 25, 2018 at 23:39

answered Feb 25, 2018 at 23:34

twain249

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1 Comment

trying to learn Over a year ago

i think if statement inside else is not neccessary since c variable is reseted if it catches an 0.

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