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# Fig10_46 - int right = left k m left right = INFINITY for...

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public class Fig10_46 { /* START: Fig10_46.txt */ public static final long INFINITY = Long.MAX_VALUE; /** * Compute optimal ordering of matrix multiplication. * c contains the number of columns for each of the n matrices. * c[ 0 ] is the number of rows in matrix 1. * The minimum number of multiplications is left in m[ 1 ][ n ]. * Actual ordering is computed via another procedure using lastChange. * m and lastChange are indexed starting at 1, instead of 0. * Note: Entries below main diagonals of m and lastChange * are meaningless and uninitialized. */ public static void optMatrix( int [ ] c, long [ ][ ] m, int [ ][ ] lastChange ) { int n = c.length - 1; for( int left = 1; left <= n; left++ ) m[ left ][ left ] = 0; for( int k = 1; k < n; k++ ) // k is right - left for( int left = 1; left <= n - k; left++ ) { // For each position

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Unformatted text preview: int right = left + k; m[ left ][ right ] = INFINITY; for( int i = left; i < right; i++ ) { long thisCost = m[ left ][ i ] + m[ i + 1 ][ right ] + c[ left - 1 ] * c[ i ] * c[ right ]; if( thisCost < m[ left ][ right ] ) // Update min { m[ left ][ right ] = thisCost; lastChange[ left ][ right ] = i; } } } } /* END */ / public static void main( String [ ] args ) { int [ ] c = { 50, 10, 40, 30, 5 }; long [ ][ ] m = new long [ 5 ][ 5 ]; int lastChange[ ][ ] = new int [ 5 ][ 5 ]; optMatrix( c, m, lastChange ); for( int i = 1; i <= 4; i++ ) { for( int j = 1; j <= 4; j++ ) System.out.print( m[ i ][ j ] + " " ); System.out.println( ); } for( int i = 1; i <= 4; i++ ) { for( int j = 1; j <= 4; j++ ) System.out.print( lastChange[ i ][ j ] + " " ); System.out.println( ); } } }...
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