Difference between revisions of "2D matrix problem"
Line 58: | Line 58: | ||
//prints a nice output for a provided line | //prints a nice output for a provided line | ||
− | public static void printLine( int[] | + | public static void printLine( int[] toPrintArray, int toPrintProd ) |
{ | { | ||
} | } | ||
Line 103: | Line 103: | ||
|Solution= | |Solution= | ||
− | To solve this problem it would be best to start by filling in the printLine method as it is useful in debugging. | + | To solve this problem it would be best to start by filling in the printLine method as it is useful in debugging. Given an array and an int this method prints the output like in my example. The main loop here should look a little strange to you. We want to print "x" between the numbers but not at the end. So we will print toPrintArray[ 0 ] first, then add a "x" and the next value in the loop. |
+ | <pre> | ||
+ | //prints a nice output for a provided line | ||
+ | //8 x 2 x 22 x 97 = 34144 | ||
+ | public static void printLine( int[] toPrintArray, int toPrintProd ) | ||
+ | { | ||
+ | System.out.print( toPrintArray[ 0 ] ); | ||
+ | |||
+ | for( int i = 1; i < toPrintArray.length; i++ ) | ||
+ | { | ||
+ | System.out.print( " x " + toPrintArray[ i ] ); | ||
+ | } | ||
+ | |||
+ | System.out.println( " = " + toPrintProd ); | ||
+ | } | ||
+ | </pre> | ||
+ | |||
+ | The next step is to fill in checkRow. Given a row and a column in the array | ||
+ | |||
+ | Now that you have list of rows printing you can write checkLine. Manually check a few lines to make sure you are getting the right results. You're almost there, fill in checkCol, checkDiagonal, and verify that you are getting the right answer. | ||
<pre> | <pre> | ||
//from (row,col) check product of the row | //from (row,col) check product of the row | ||
Line 124: | Line 143: | ||
</pre> | </pre> | ||
− | + | ||
|SolutionCode= | |SolutionCode= | ||
Line 177: | Line 196: | ||
//prints a nice output for a provided line | //prints a nice output for a provided line | ||
− | public static void printLine( int[] | + | //8 x 2 x 22 x 97 = 34144 |
+ | public static void printLine( int[] toPrintArray, int toPrintProd ) | ||
{ | { | ||
− | for( int i = | + | System.out.print( toPrintArray[ 0 ] ); |
+ | |||
+ | for( int i = 1; i < toPrintArray.length; i++ ) | ||
{ | { | ||
− | System.out.print( | + | System.out.print( " x " + toPrintArray[ i ] ); |
} | } | ||
+ | |||
+ | System.out.println( " = " + toPrintProd ); | ||
} | } | ||
Line 262: | Line 286: | ||
Output | Output | ||
====== | ====== | ||
− | + | 66 x 91 x 88 x 97 = 51267216 | |
− | 66 91 88 97 | + | |
</pre> | </pre> | ||
}} | }} |
Revision as of 02:19, 9 April 2010
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ProblemThis problem is a simplified version of problem 11 on projecteuler.net. Using the provided array find the 4 numbers along a row, column or diagonal with the greatest product. I have included some skeleton code to make problem a little easier. For example at row 0, column 0 there are three lines to check.
public class matrix { static final int lineLength = 4; //length of line to check static int[] bestNumbers = new int[lineLength]; //best line found so far static int bestNumber = 0; //product of the best line static final int array[][] ={ { 8, 2,22,97,38,15, 0,40, 0,75, 4, 5, 7,78,52,12,50,77,91, 8}, {49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48, 4,56,62, 0}, {81,49,31,73,55,79,14,29,93,71,40,67,53,88,30, 3,49,13,36,65}, {52,70,95,23, 4,60,11,42,69,24,68,56, 1,32,56,71,37, 2,36,91}, {22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80}, {24,47,32,60,99, 3,45, 2,44,75,33,53,78,36,84,20,35,17,12,50}, {32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70}, {67,26,20,68, 2,62,12,20,95,63,94,39,63, 8,40,91,66,49,94,21}, {24,55,58, 5,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72}, {21,36,23, 9,75, 0,76,44,20,45,35,14, 0,61,33,97,34,31,33,95}, {78,17,53,28,22,75,31,67,15,94, 3,80, 4,62,16,14, 9,53,56,92}, {16,39, 5,42,96,35,31,47,55,58,88,24, 0,17,54,24,36,29,85,57}, {86,56, 0,48,35,71,89, 7, 5,44,44,37,44,60,21,58,51,54,17,58}, {19,80,81,68, 5,94,47,69,28,73,92,13,86,52,17,77, 4,89,55,40}, {04,52, 8,83,97,35,99,16, 7,97,57,32,16,26,26,79,33,27,98,66}, {88,36,68,87,57,62,20,72, 3,46,33,67,46,55,12,32,63,93,53,69}, {04,42,16,73,38,25,39,11,24,94,72,18, 8,46,29,32,40,62,76,36}, {20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74, 4,36,16}, {20,73,35,29,78,31,90, 1,74,31,49,71,48,86,81,16,23,57, 5,54}, {01,70,54,71,83,51,54,69,16,92,33,48,61,43,52, 1,89,19,67,48} }; public static void main(String[] args) { for( int row = 0; row < array[0].length; row++ ) { for( int col = 0; col < array.length; col++ ) { checkRow( row, col ); checkCol( row, col ); checkDiagonal( row, col ); } } System.out.println( "WINNER!! " + bestNumber ); printLine( bestNumbers ); } //prints a nice output for a provided line public static void printLine( int[] toPrintArray, int toPrintProd ) { } //calculate the product for the line passed //if it the product is better than bestNumber update it public static void checkLine( int[] toCheck ) { } //from (row,col) check product of the row public static void checkRow( int row, int col ) { int[] tempRow = new int[ 4 ]; ... checkLine( tempRow ); } //from (row,col) check product of the column public static void checkCol( int row, int col ) { int[] tempRow = new int[ 4 ]; ... checkLine( tempRow ); } //from (row,col) check product of the diagonal public static void checkDiagonal( int row, int col ) { int[] tempRow = new int[ 4 ]; ... checkLine( tempRow ); } } |
More with Arrays
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SolutionTo solve this problem it would be best to start by filling in the printLine method as it is useful in debugging. Given an array and an int this method prints the output like in my example. The main loop here should look a little strange to you. We want to print "x" between the numbers but not at the end. So we will print toPrintArray[ 0 ] first, then add a "x" and the next value in the loop. //prints a nice output for a provided line //8 x 2 x 22 x 97 = 34144 public static void printLine( int[] toPrintArray, int toPrintProd ) { System.out.print( toPrintArray[ 0 ] ); for( int i = 1; i < toPrintArray.length; i++ ) { System.out.print( " x " + toPrintArray[ i ] ); } System.out.println( " = " + toPrintProd ); } The next step is to fill in checkRow. Given a row and a column in the array Now that you have list of rows printing you can write checkLine. Manually check a few lines to make sure you are getting the right results. You're almost there, fill in checkCol, checkDiagonal, and verify that you are getting the right answer. //from (row,col) check product of the row public static void checkRow( int row, int col ) { //make sure the row we are checking does not exceed the array row length if( col + lineLength <= array[0].length ) { int[] tempRow = new int[ 4 ]; for( int i = 0; i < lineLength; i++ ) { tempRow[ i ] = array[ row ][ col + i ]; } checkLine( tempRow ); } }//checkRow | ||
Code |