class Edge {    enum Type {        inner, outer, flat    }     Piece parent;    Type type;     boolean fitsWith(Edge type) {    }; // Inners & outer fit together.} class Piece {    Edge left, right, top, bottom;     // 90, 180, etc    Orientation solvedOrientation = 90;} class Puzzle {    // Remaining pieces left to put away.    Piece[][] pieces;    Piece[][] solution;    Edge[] inners, outers, flats;     // We‘re going to solve this by working our way    // in-wards, starting with the corners.    // This is a list of the inside edges.    Edge[] exposed_edges;     void sort() {         // Iterate through all edges,        // adding each to inners, outers, etc,        // as appropriate.        // Look for the corners—add those to solution.        // Add each non-flat edge of the corner        // to exposed_edges.     }     void solve() {        for (Edge edge1 : exposed_edges) {            // Look for a match to edge1            if (edge1.type == Edge.Type.inner) {                for (Edge edge2 : outers) {                    if (edge1.fitsWith(edge2)) {                        // We found a match!                        // Remove edge1 from                        // exposed_edges.                        // Add edge2‘s piece                        // to solution.                        // Check which edges of edge2                        // are exposed, and add                        // those to exposed_edges.                    }                }                // Do the same thing,                // swapping inner & outer.            }        }    }}