-- May 4 In-Class Exercise Thread
Possible triangles:
I. Triangle (1, 2, 4)
d(1,1) + d(4,2) >= d(4,2)
1+ 2 >= 2
d(1,2) + d(2,4) >= d(1,4)
1 + 2 >= 3
d(1,4) + d(4,2) >= d(1,2)
3 + 2 >= 1
Each edge obeys triangle inequality
II. (Triangle 2, 3, 4)
d(2,3) + d(2,4) >= d(3,4)
1+ 2 >= 1
d(2,3) + d(3,4) >= d(2,4)
1 + 1 >= 2
d(2,4) + d(3, 4) >= d(2,3)
2 + 1 >= 1
Each edge obeys triangle inequality
III. Triangle (1, 3, 4)
d(1,3) + d(1,4) >= d(4,3)
2 + 3 >= 1
d(1,3) + d(3, 4) >= d(1,4)
2 + 1 >= 3
d(1,4) + d(3,4) >= d(1,3)
3+ 1 >= 2
Each edge obeys triangle inequality
IV. Triangle (1, 2, 3)
d(2,3) + d(1, 3) >= d(1,2)
1 + 2 >= 1
d(1,2) + d(2,3) >= d(1,3)
1 + 1 >= 2
d(1,2) + d(1,3) >= d(3,2)
1+ 2 >= 1
Each edge obeys triangle inequality
APPROX-TSP-TOUR:
(root = v1)
Q = MAKE-QUEUE(G.V)
[1, 0, 0
2, inf, NIL
3, inf, NIL
4, inf, NIL]
Q!=0 - (1)
U = 1,0,0
V = 2 , 0+1 < inf, true
V = 3 , 0+2 < inf, true
V = 4 , 0+3 < inf, true
Q = MAKE-QUEUE(G.V)
[2, 1, 1
3, 2, 1
4, 3, 1]
Q!=0 - (2)
U = 2,1,1
V = 3 , 1+1 < 2, true
V = 4 , 1+2 < 3, false
Q = MAKE-QUEUE(G.V)
[3, 2, 1
4, 3, 1]
Q!=0 - (3)
U = 3,1,1
V = 4 , 1+2 < 3, false
Q = MAKE-QUEUE(G.V)
[4, 3, 1]
Q!=0 - (4)
U = 4,3,1
V = empty set
MST-PRIM => {1,2,3,4}
Thus, traversal order => 1,2,3,4
traversal cost = 1+1+1+3 = 6
<pre>
Possible triangles:
I. Triangle (1, 2, 4)
d(1,1) + d(4,2) >= d(4,2)
1+ 2 >= 2
d(1,2) + d(2,4) >= d(1,4)
1 + 2 >= 3
d(1,4) + d(4,2) >= d(1,2)
3 + 2 >= 1
Each edge obeys triangle inequality
II. (Triangle 2, 3, 4)
d(2,3) + d(2,4) >= d(3,4)
1+ 2 >= 1
d(2,3) + d(3,4) >= d(2,4)
1 + 1 >= 2
d(2,4) + d(3, 4) >= d(2,3)
2 + 1 >= 1
Each edge obeys triangle inequality
III. Triangle (1, 3, 4)
d(1,3) + d(1,4) >= d(4,3)
2 + 3 >= 1
d(1,3) + d(3, 4) >= d(1,4)
2 + 1 >= 3
d(1,4) + d(3,4) >= d(1,3)
3+ 1 >= 2
Each edge obeys triangle inequality
IV. Triangle (1, 2, 3)
d(2,3) + d(1, 3) >= d(1,2)
1 + 2 >= 1
d(1,2) + d(2,3) >= d(1,3)
1 + 1 >= 2
d(1,2) + d(1,3) >= d(3,2)
1+ 2 >= 1
Each edge obeys triangle inequality
APPROX-TSP-TOUR:
(root = v1)
Q = MAKE-QUEUE(G.V)
[1, 0, 0
2, inf, NIL
3, inf, NIL
4, inf, NIL]
Q!=0 - (1)
U = 1,0,0
V = 2 , 0+1 < inf, true
V = 3 , 0+2 < inf, true
V = 4 , 0+3 < inf, true
Q = MAKE-QUEUE(G.V)
[2, 1, 1
3, 2, 1
4, 3, 1]
Q!=0 - (2)
U = 2,1,1
V = 3 , 1+1 < 2, true
V = 4 , 1+2 < 3, false
Q = MAKE-QUEUE(G.V)
[3, 2, 1
4, 3, 1]
Q!=0 - (3)
U = 3,1,1
V = 4 , 1+2 < 3, false
Q = MAKE-QUEUE(G.V)
[4, 3, 1]
Q!=0 - (4)
U = 4,3,1
V = empty set
MST-PRIM => {1,2,3,4}
Thus, traversal order => 1,2,3,4
traversal cost = 1+1+1+3 = 6
</pre>