The Frequency Bounds for Travelling Salesman Problem Based on Frequency Quadrilaterals
摘要
Given a weighted graph for TSP, a corresponding frequency graph is computed using the optimal paths with given endpoints (optimal paths for short). The edges in optimal Hamiltonian cycle (OHC) show special frequencies much bigger than those of most other edges. The average frequencies for edges and paths in OHC are studied as a frequency graph is computed based upon the frequency quadrilaterals or optimal 4-vertex paths. The lower frequency bounds for an OHC edge, two and three immediate OHC edges are proven to be 35/9, 22/3 and 35/3, respectively in the worst average case. Moreover, the average frequency for all OHC edges is bigger than 4 and it is bigger than 13/3 for big and large TSP. These findings are verified with experimental results.