Weight Distributions of Two Classes of Linear Codes with Five or Six Weights

In this paper, based on the theory of defining sets, two classes of five-weight or six-weight linear codes over Fp are constructed. The weight distributions of the linear codes are determined by means of Weil sums and a new type of exponential sums. In some case, there is an almost optimal code with respect to Griesmer bound, which is also an optimal one according to the online code table.