The Lieb-Liniger model describes N bosons in 1D interacting via delta-function repulsion: H = −Σ∂²_i + 2c·Σ_{i<j}δ(x_i−x_j). The dimensionless coupling γ = c/n controls the regime: γ≪1 is weakly-interacting (quasi-BEC), γ≫1 is the Tonks-Girardeau fermionized limit. The ground-state energy per particle e(γ) = n²·ε(γ) is computed via Bethe ansatz integral equations.