Fig. 3.

An example for the $O(K)$ merge algorithm. Solid circles indicate the score vectors of list 1, and open circles are those of list 2. The numbers indicate the order in the sorted list of the union of the two lists. We sequentially delete dominated solutions during scanning of the sorted list. In this example, by scanning score vectors 1 to 9, we remove score vectors 4, 5, and 8.