feat coordinate

app/src/main/java/sudoku/Sudoku.java

@@ -55,4 +55,64 @@ public class Sudoku {
 		}
 		return mutableCells;
 	}
+
+	public boolean contains(Cell cell) {
+		return this.cells.contains(cell);
+	}
+
+	private Coordinate getCoordinateCell(Cell c) throws Exception {
+		int x=0, y=0;
+		int size = this.getSize();
+
+		if (!this.contains(c)) {
+			throw new Exception("The given cell is not in this sudoku.");
+		}
+
+		for (Cell cell : this.cells) {
+			if (cell == c){
+				return new Coordinate(x, y);
+			}
+			if (x == size - 1){
+				y+=1;
+				x=0;
+			}
+			else {
+				x+=1;
+			}
+		}
+		return new Coordinate(x, y);
+	}
+
+    public void updateSymbolsPossibilities() throws Exception {
+		for (IConstraint constraint : constraints) {
+			List<MutableCell> mutableCells = this.getMutableCells();
+			for (MutableCell cell : mutableCells) {
+                Coordinate coord = null;
+                try {
+                    coord = this.getCoordinateCell(cell);
+                } catch (Exception e) {
+                    throw new RuntimeException(e);
+                }
+                constraint.getPossibleSymbols(this, coord.getX(), coord.getY());
+				if (cell.getPossibleSymbols().isEmpty()){
+					throw new Exception("Rollback bitch");
+				}
+			}
+		}
+	}
+
+	public String toString (){
+		StringBuilder sb = new StringBuilder();
+		sb.append("Sudoku {");
+		for (int i = 0; i < getSize(); i++) {
+			sb.append("\n\t");
+			for (int j = 0; j < getSize(); j++) {
+				Cell cell = getCell(i, j);
+				sb.append(cell.toString()).append(" ");
+			}
+		}
+		sb.append("\n}");
+		return sb.toString();
+	}
+
 }