Broken hyperlinks

[ndsvw]

Hi, I found some broken hyperlinks:

• preview.md (file: CONTRIBUTING.md, status code: 404)

These ones do maybe/probably work on the website, but not on GitHub, because of the absolute path:

• /data_structures/sqrt_decomposition.html (file: src/data_structures/sqrt-tree.md, status code: 400)
• /data_structures/segment_tree.html (file: src/others/josephus_problem.md, status code: 400)
• /string/string-hashing.html (file: src/string/manacher.md, status code: 400)
• /string/suffix-tree-ukkonen.html (file: src/string/manacher.md, status code: 400)
• /string/z-function.html (file: src/string/manacher.md, status code: 400)

External hyperlinks:

• https://codingcompetitions.withgoogle.com/codejam/round/0000000000051635/0000000000104f1a#problem (file: src/algebra/chinese-remainder-theorem.md, status code: 404)
• https://codingcompetitions.withgoogle.com/codejam/round/0000000000051679/0000000000146184 (file: src/algebra/continued-fractions.md, status code: 404)
• https://devskill.com/CodingProblems/ViewProblem/61 (file: src/combinatorics/binomial-coefficients.md, status code: 404)
• https://devskill.com/CodingProblems/ViewProblem/255 (file: src/combinatorics/binomial-coefficients.md, status code: 404)
• http://esci.ru/ttb/statement-62.htm (file: src/combinatorics/inclusion-exclusion.md, status code: 404)
• https://icpcarchive.ecs.baylor.edu/index.php?option=onlinejudge&page=show_problem&problem=2609 (file: src/dynamic_programming/profile-dynamics.md, error: ECONNRESET)
• https://code.google.com/codejam/contest/311101/dashboard#s=a&a=1 (file: src/geometry/nearest_points.md, status code: 404)
• https://sites.math.washington.edu/~billey/classes/562.winter.2018/articles/GraphTheory.pdf (file: src/geometry/planar.md, status code: 404)
• https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1851 (file: src/graph/dijkstra.md, error: ECONNRESET)
• https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=820 (file: src/graph/dijkstra.md, error: ECONNRESET)
• https://devskill.com/CodingProblems/ViewProblem/79 (file: src/graph/strongly-connected-components.md, status code: 404)
• https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&category=720&page=show_problem&problem=5524 (file: src/string/suffix-array.md, error: ECONNRESET)
• https://icpcarchive.ecs.baylor.edu/index.php?option=onlinejudge&Itemid=8&page=show_problem&problem=1944 (file: src/string/suffix-array.md, error: ECONNRESET)
• https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=2514 (file: src/string/suffix-array.md, error: ECONNRESET)
• https://icpcarchive.ecs.baylor.edu/index.php?option=onlinejudge&page=show_problem&problem=4868 (file: src/string/suffix-array.md, error: ECONNRESET)

[jakobkogler]

I've fixed a couple of the links.

For the GCJ problems: Google stopped doing the contest, but they published all historical problems here: https://github.com/google/coding-competitions-archive

For the DevSkills problems: You can see them still on archive.org , but the website changed a lot and it's no longer to see/access those problems (at least not without registering). So I think we should remove them. Not sure about their quality also, and since it's not possible to submit it doesn't make much sense to keep them.
We also have a lot of other DevSkills links that already point to archive.org. I think we can also remove them.

[Ojaswa-Yadav]

/resolve