The contributions of the co-authors are as follows:• I proposed the method, conducted experiments and wrote the manuscript draft. The other authors gave me valuable advice at every stage. • Prof. Zhang, Yaoxin Wu and Zhiguang Cao suggested the project direction and polished the manuscript. Chapter 4 is published as Yuan Jiang, Zhiguang Cao, Yaoxin Wu, Jie Zhang. Multi-View Graph Contrastive Learning for Solving Vehicle Routing Problems. 39th Conference on Uncertainty in Artificial Intelligence, 2023. The contributions of the co-authors are as follows: • I proposed the method, conducted experiments and wrote the manuscript draft. Prof. Zhang, Yaoxin Wu and Zhiguang Cao gave me valuable advice for preparing the manuscript. Yaoxin Wu and Zhiguang Cao helped polish the manuscript. Chapter 5 is submitted to Yuan Jiang, Zhiguang Cao, Yaoxin Wu, Wen Song, Jie Zhang. Ensemble-based Deep Reinforcement Learning for Vehicle Routing Problems under Distribution Shift. 37th International Conference on Advances in Neural Information Processing Systems, 2023. The contributions of the co-authors are as follows:• I proposed the method, conducted experiments and wrote the manuscript draft. Prof. Zhang, Zhiguang Cao, Wen Song provided me with valuable comments to prepare the manuscript. Zhiguang Cao, Wen Song and Yaoxin Wu helped polish the manuscript.