Waltz’s Algorithm
1. Find borders and label them: border has no vertices outside it.
2. Number vertices to be traversed in order:
a. Number boundary vertices first.
b. Number interior vertices by moving from a numbered vertex
toward an adjacent unnumbered one.
3. Now visit each vertex V in order and attempt to label:
a. Attach all physically possible labels of type V.
b. For each vertex A adjacent to V and already visited, eliminate
from V any labeling for which there is no consistent label at A.
c. For each vertex adjacent to A visited in step b, do:
i. Eliminate labels inconsistent with V.
ii.If any eliminated, propagate constraints to neighbors of A.
iii. Continue to propagate until there are no adjacent
labeled vertices or no change made to a set.