Added cofactor function

src/main/java/com/mattrixwv/matrix/IntegerMatrix.java

@@ -656,6 +656,32 @@ public class IntegerMatrix{
 		//Return the determinant
 		return det;
 	}
+	public IntegerMatrix cofactor(){
+		//Make sure the matrix is square
+		if(!isSquare()){
+			throw new InvalidGeometryException("A matrix must be square to find the cofactor matrix");
+		}
+
+		//Create a new grid
+		int[][] newGrid = new int[getNumRows()][getNumCols()];
+		//If the grid is 1x1 return the grid
+		if(getNumRows() == 1){
+			newGrid[0][0] = grid[0][0];
+		}
+		//Use the formula to find the cofactor matrix
+		else{
+			for(int row = 0;row < getNumRows();++row){
+				int multiplier = ((row % 2) == 0) ? 1 : -1;
+				for(int col = 0;col < getNumCols();++col){
+					newGrid[row][col] = multiplier * laplaceExpansionHelper(row, col).determinant();
+					multiplier = -multiplier;
+				}
+			}
+		}
+
+		//Return the new matrix
+		return new IntegerMatrix(newGrid);
+	}
 
 	//Object funtions
 	@Override