double astrix 2D array signature question..
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Thread: double astrix 2D array signature question..

  1. #1
    Join Date
    Jan 2009
    Posts
    156

    double astrix 2D array signature question..

    its a question from a test:
    i was asks what what1(arr,6,5) expression will return
    ??
    arr is a 2D array which looks like this:
    0 1 1 0 1
    0 0 1 0 0
    0 0 1 1 1
    0 1 0 0 0
    1 0 0 1 1
    1 0 1 1 0

    Code:
    int what1(int **arr, int m, int n){
    int i, j, tmp, stam=0;
    
    for(i=0; i<m; i++)
    for(j=0; j<n; j++){
       tmp = what2(arr,i,j,m,n);
       if (tmp>stam) 
             stam = tmp;
    }
    return stam;
    }
    
    int what2 (int **arr, int row, int col, int m, int n){
    int i,j,tmp, stam=0;
    
    if (row < 0 || row >= m || col < 0 || col >= n) return 0;
    if (arr[row][col] == 0) return 0;
    
    arr[row][col] = 0;
    for(i=-1; i<2; i++)
    	for(j=-1; j<2; j++){
    		if(!i && !j) continue;
    tmp = 1 + what2(arr, row+i, col+j, m, n);
    		if (tmp > stam)  stam = tmp;
    	}
    arr[row][col] = 1;
    
    return stam;
    }
    why it passes the arr as
    what1(arr,6,5) instead of what1(&arr,6,5)

    can i do arr[0][0] = 0; for arr
    if arr is passed instead of &arr
    will it save the change after the function ends??

    what2
    has that line
    Code:
    arr[row][col] = 0;
    and i cant decide what happens at the beginning when arr[0][0] = 0;
    because arr is passed not &arr
    so the change which that line will make
    will not exist after what2 ends
    ??

  2. #2
    Lindley is offline Elite Member Power Poster
    Join Date
    Oct 2007
    Location
    Fairfax, VA
    Posts
    10,888

    Re: double astrix 2D array signature question..

    what1(arr,6,5) instead of what1(&arr,6,5)
    You say arr is a 2D array, presumably of type int**. what1 expects an int**. Why would you expect to be passing an int*** instead?

  3. #3
    Join Date
    Jan 2009
    Posts
    156

    Re: double astrix 2D array signature question..

    because
    &arr is the way we pass double astrix variable
    so we could make changes on the arr itself
    ??

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