2021: d01: ex2: add solution

.envrc

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+use_flake() {
+  watch_file flake.nix
+  watch_file flake.lock
+  eval "$(nix print-dev-env)"
+}
+
+use flake

.gitignore

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+# Generated by Nix
+/.pre-commit-config.yaml

2021/d01/ex1/ex1.py

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+#!/usr/bin/env python
+
+import itertools
+import sys
+from typing import List
+
+
+def solve(input: List[int]) -> int:
+    return sum(prev < cur for (prev, cur) in itertools.pairwise(input))
+
+
+def main() -> None:
+    input = [int(line) for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()

2021/d01/ex2/ex2.py

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+#!/usr/bin/env python
+
+import collections
+import itertools
+import sys
+from typing import List
+
+
+def sliding_window(iterable, n):
+    it = iter(iterable)
+    window = collections.deque(itertools.islice(it, n), maxlen=n)
+    if len(window) == n:
+        yield tuple(window)
+    for x in it:
+        window.append(x)
+        yield tuple(window)
+
+
+def solve(input: List[int]) -> int:
+    windowed = [sum(window) for window in sliding_window(input, 3)]
+    return sum(prev < cur for (prev, cur) in itertools.pairwise(windowed))
+
+
+def main() -> None:
+    input = [int(line) for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()

flake.lock

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+{
+  "nodes": {
+    "futils": {
+      "locked": {
+        "lastModified": 1638122382,
+        "narHash": "sha256-sQzZzAbvKEqN9s0bzWuYmRaA03v40gaJ4+iL1LXjaeI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "74f7e4319258e287b0f9cb95426c9853b282730b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "ref": "master",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1638286143,
+        "narHash": "sha256-A+rgjbIpz3uPRKHPXwdmouVcVn5pZqLnaZHymjkraG4=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "29d1f6e1f625d246dcf84a78ef97b4da3cafc6ea",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "pre-commit-hooks": {
+      "inputs": {
+        "flake-utils": [
+          "futils"
+        ],
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1637745948,
+        "narHash": "sha256-DmQG1bZk24eS+BAHwnHPyYIadMLKbq0d1b//iapYIPU=",
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "c3b4f94350b0e59c2546fa85890cc70d03616b9c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "ref": "master",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "futils": "futils",
+        "nixpkgs": "nixpkgs",
+        "pre-commit-hooks": "pre-commit-hooks"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "Advent of Code answers";
+
+  inputs = {
+    futils = {
+      type = "github";
+      owner = "numtide";
+      repo = "flake-utils";
+      ref = "master";
+    };
+
+    nixpkgs = {
+      type = "github";
+      owner = "NixOS";
+      repo = "nixpkgs";
+      ref = "nixos-unstable";
+    };
+
+    pre-commit-hooks = {
+      type = "github";
+      owner = "cachix";
+      repo = "pre-commit-hooks.nix";
+      ref = "master";
+      inputs = {
+        flake-utils.follows = "futils";
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
+  };
+
+  outputs = { self, futils, nixpkgs, pre-commit-hooks }:
+    futils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        checks = {
+          pre-commit = pre-commit-hooks.lib.${system}.run {
+            src = self;
+
+            hooks = {
+              black = {
+                enable = true;
+              };
+
+              isort = {
+                enable = true;
+              };
+
+              nixpkgs-fmt = {
+                enable = true;
+              };
+            };
+          };
+        };
+
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            python310 # Latest version at the moment
+          ];
+
+          inherit (self.checks.${system}.pre-commit) shellHook;
+        };
+      });
+}