[ymeng] linked-list: extract 'insert root' to individual method
[ymeng] permutation: build structure
[ymeng] build matcher to permutation result
[ymeng] permutation: permutate whole word that does not contain duplicated characters
[ymeng] permutation: permutate partial word that does not contain duplicated characters
[ymeng] permutation: permutate word that contains duplicated characters
[ymeng] generic quick sort
[ymeng] permutation: implements all function with iterative method
[ymeng] extract sort method to utils package
[ymeng] fix unsafe operation
[ymeng] move generic swap to utils package