  After reducing the undirected Hamiltonian cycle problem into the TSP problem
with cost 0 or 1, we developed an effective algorithm to compute the optimal
tour of the transformed TSP. Our algorithm is described as a growth process:
initially, constructing 4-vertexes optimal tour; next, one new vertex being
added into the optimal tour in such a way to obtain the new optimal tour; then,
repeating the previous step until all vertexes are included into the optimal
tour. This paper has shown that our constructive algorithm can solve the
undirected Hamiltonian cycle problem in polynomial time. According to
Cook-Levin theorem, we argue that we have provided a constructive proof of
P=NP.
