Java int[][] array - iterating and finding value?

You can iterate with either for loops or enhanced for loops: for (int row=0; row This // is the *whole* row, not the row *number*. For (int row : grid) { for (int value : row) { // Do stuff } } The first version would be the easiest solution to the "find the co-ordinates" question - just check whether the value in the inner loop is correct.

1 for completeness but I would rename 'i' and 'j' to 'row' and 'col'. – Outlaw Programmer Jan 23 '09 at 20:55 Oh, okay then :) Now watch me fail to do it consistently... – Jon Skeet Jan 23 '09 at 20:56 1 But Outlaw, if he does that, he won't be paying homage to Fortran. – Paul Tomblin Jan 23 '09 at 20:57 @Paul: Nah.

Fortran was paying homage to this answer's first version. It may not have known it, but it's surely true. – Jon Skeet Jan 23 '09 at 21:00 @Outlaw ... except which dimension is the rows and which dimension is the columns is totally dependent on your interpretation (maprowcolumn or mapcolumnrow); however, i, j, k, l, m... are always silly_arrayijklm.... Which I suppose is what Jon was getting at.

– Aaron Maenpaa Jan 23 '09 at 21:02.

To iterate over the values use loops: int matrix //... for(int row : matrix) for(int cell : row){ //do something with cell } to access the coordinates based on the value you would need some sort of double hashmap (look a at java.util. HashMap) but I am aware of nothing that does so directly.

You could do it with a regular hashmap. You'd just need to define an object to use as the Key that has both coordinates in it. – Herms Jan 23 '09 at 20:53 @Herms :He wanats to find the coordinates by the value.So the key must be the cell value .

Things will get more complicated if multiple cells can have the same value, but it is still doable – user54579 Jan 23 '09 at 20:56 I think having another datastructure here is probably a bad idea. It might be tough to keep them in sync.It's probably better to search the whole table, even though it will be slower. – Outlaw Programmer Jan 23 '09 at 21:02 Store new Integer(ix + iy * 1000) as the value in your hash table.

If your y index can go over 1000 use a bigger number--ints are really big.To get it back use ix=val%1000, iy=val/1000. – Bill K Jan 23 '09 at 21:22.

Unless your grid is sorted in some way then you probably won't do any better than a brute force search. For iterating, I think it would be something like this (syntax might be off a bit, I haven't dealt with arrays in java for a while. ): int grid; // just assuming this is already assigned somewhere for(int x = 0 ; x Length ; x++) { int row = gridx; for(int y = 0 ; y.

To iterate over all the elements in the grid try this: int grid = new int1010; for(int I = 0; I.

Use nested for loops to iterate over the x and y dimensions, which lets you go over each value, one at a time. For inputting a value, just do the same as above, but look for a match to your requested value.

You'll be happiest if you block all these collections inside a single class and don't expose them in any way. This means moving your search and lookup routines into this class as well. For storage, everybody's covered iterating, add a hashtable and a lookup.

I put this comment on nickolai's post: Store new Integer(ix + iy * 1000) as the value in your hash table. If your y index can go over 1000 use a bigger number--ints are really big. To get it back use ix=val%1000, iy=val/1000.

If your array and hashtable are encapsulated in the same class, the rest of your code will be pretty easy to write and a lot cleaner.

There's generally no way to find the specific coordinates of a particular value except by going through the array and searching for it. However, if the values in the array are guaranteed to be unique (i.e. Each value only occurs in one cell), you could maintain a separate array as an index, which stores the coordinates of each value indexed by the value.

Misleading, a hashtable does it easily. – Bill K Jan 23 '09 at 21:24.

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