matrix chain bottom up failed

Author: dheeraj9198

src/dymanicProgramming/MatrixChainMultiplication.java

@@ -7,7 +7,7 @@ public class MatrixChainMultiplication {
 
     private static Integer[][] solMat;
 
-    private static int matrixChainOrder(int[] ints, int start, int end) {
+    private static int matrixChainOrderTopDown(int[] ints, int start, int end) {
         if (solMat[start][end] != null) {
             return solMat[start][end];
         }
@@ -17,9 +17,9 @@ private static int matrixChainOrder(int[] ints, int start, int end) {
         } else {
             int min = Integer.MAX_VALUE;
             for (int temp = start; temp < end; temp++) {
-                int prev = matrixChainOrder(ints, start, temp);
-                int next = matrixChainOrder(ints, temp + 1, end);
-                int current = ints[start-1] * ints[temp] * ints[end];
+                int prev = matrixChainOrderTopDown(ints, start, temp);
+                int next = matrixChainOrderTopDown(ints, temp + 1, end);
+                int current = ints[start - 1] * ints[temp] * ints[end];
                 int count = prev + next + current;
                 min = Math.min(min, count);
             }
@@ -29,9 +29,35 @@ private static int matrixChainOrder(int[] ints, int start, int end) {
         return sol;
     }
 
+
+    private static int bottomUp(Integer[][] ints, int[] arr) {
+        for (int k = 1; k < ints.length; k++) {
+            ints[k][k] = 0;
+        }
+        for (int end = 2; end < ints[0].length; end++) {
+            int startTemp = 1;
+            for (int endTemp = end; endTemp < ints[0].length; endTemp++) {
+                int min = Integer.MAX_VALUE;
+                for (int k = startTemp; k < endTemp; k++) {
+                    int current = arr[startTemp - 1] * arr[k] * arr[end];
+                    int count = ints[startTemp][k] + ints[k + 1][endTemp] + current;
+                    min = Math.min(min, count);
+                }
+                ints[startTemp][end] = min;
+                startTemp++;
+            }
+        }
+        return ints[1][arr.length - 1];
+    }
+
     public static void main(String[] strings) {
-        int arr[] = {1, 2, 3, 4, 5};
+        int arr[] = {1, 2, 3, 4};
         solMat = new Integer[arr.length][arr.length];
-        System.out.println("Minimum number of multiplications is " + matrixChainOrder(arr, 1, arr.length - 1));
+/*
+        System.out.println("Minimum number of multiplications is " + matrixChainOrderTopDown(arr, 1, arr.length - 1));
+*/
+
+        System.out.println("Minimum number of multiplications is " + bottomUp(solMat,arr));
+
     }
 }

src/dymanicProgramming/prereq/DiagonalTraversalOfMatrix.java

@@ -0,0 +1,43 @@
+package dymanicProgramming.prereq;
+
+/**
+ * Created by dheeraj on 7/18/2016.
+ * needed for filling matrix chain
+ */
+public class DiagonalTraversalOfMatrix {
+
+    private static void printDiagonal(int[][] ints) {
+        int row = 1;
+        int col = 2;
+        while (col < ints[0].length) {
+            int rowTemp = row;
+            int colTemp = col;
+            while (colTemp < ints[0].length) {
+                System.out.print(ints[rowTemp][colTemp] + " ");
+                rowTemp++;
+                colTemp++;
+            }
+            row++;
+            col = row + 1;
+        }
+    }
+
+    private static void printDiagonalOpt(int[][] ints) {
+        for (int col =2;col < ints[0].length;col++) {
+            int rowTemp = 1;
+            for (int colTemp = col;colTemp < ints[0].length;colTemp++) {
+                System.out.print(ints[rowTemp][colTemp] + " ");
+                rowTemp++;
+            }
+        }
+    }
+
+    public static void main(String[] strings) {
+        int[][] mat = new int[][]{
+                {1, 2, 3, 4},
+                {5, 6, 7, 8},
+                {9, 10, 11, 12},
+                {13, 14, 15, 16}};
+        printDiagonal(mat);
+    }
+}