Thus 3.13A is only one of 2520 ways of connecting the solution shown in Figure eight cities. Given that the distances in Figure 3.13 are the appropriate map units to be minimized, then we can reduce the of alternative solutions range very substantially by using two theorems (1) The optimal tour does not intersect itself since any two intersecting links can always be replaced by two non-int links of a shorter total distance (compare Figures 3.13A and B) f we form a convex polygon or hull bounding the points to be connected (2) Figure 3.13c, then the points which form its vertices occur in the same order on the optimal tour as they do on the convex hull. The effect of these two theorems is greatly to reduce the number of shortest path tours which are worth Instead of (3.9), the number of tours is considering. reduced to
(n--1)!/(m --1)!