Cracking the Coding Interview - Fooo

Solutions to Chapter 7 | Object Oriented Design
7 6 Implement a jigsaw puzzle Design the data structures and explain an algorithm to
solve the puzzle
SOLUTION
1 5 9
Cracking the Coding Interview | Concepts and Algorithms
pg 62
1 class Edge {
2 enum Type { inner, outer, flat }
3 Piece parent;
4 Type type;
5 bool fitsWith(Edge type) { ... }; // Inners & outer fit together.
6 }
7 class Piece {
8 Edge left, right, top, bottom;
9 Orientation solvedOrientation = ...; // 90, 180, etc
10 }
11 class Puzzle {
12 Piece[][] pieces; /* Remaining pieces left to put away. */
13 Piece[][] solution;
14 Edge[] inners, outers, flats;
15 /* We’re going to solve this by working our way in-wards, starting
16 * with the corners. This is a list of the inside edges. */
17 Edge[] exposed_edges;
18
19 void sort() {
20 /* Iterate through all edges, adding each to inners, outers,
21 * etc, as appropriate. Look for the corners—add those to
22 * solution. Add each non-flat edge of the corner to
23 * exposed_edges. */
24 }
25
26 void solve() {
27 foreach edge1 in exposed_edges {
28 /* Look for a match to edge1 */
29 if (edge1.type == Edge.Type.inner) {
30 foreach edge2 in outers {
31 if edge1.fitsWith(edge2) {
32 /* We found a match! Remove edge1 from
33 * exposed_edges. Add edge2’s piece to
34 * solution. Check which edges of edge2 are
35 * exposed, and add those to exposed_edges. */
36 }
37 }
38 /* Do the same thing, swapping inner & outer. */
39 }
40 }