Solve day01 challenge

.envrc

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+use flake .#

.gitignore

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+/target
+result
+flamegraph.svg
+.direnv

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day01"
+version = "0.1.0"

Cargo.toml

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+[workspace]
+members = [ "day01" ]
+
+[profile.release]
+panic = "abort"
+strip = "symbols"
+lto = true
+codegen-units = 1

day01/Cargo.toml

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+[package]
+name = "day01"
+version = "0.1.0"
+edition = "2021"
+
+[package.metadata.nix]
+build = true
+app = true
+
+[dependencies]

day01/input.test

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+1000
+2000
+3000
+
+4000
+
+5000
+6000
+
+7000
+8000
+9000
+
+10000

day01/src/main.rs

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+//! Find the elves carrying the most calories.
+use std::{
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+fn either_calories_or_blank(inp: String) -> Option<usize> {
+    inp.parse().ok()
+}
+
+#[derive(Default)]
+struct TopThree {
+    first: usize,
+    second: usize,
+    third: usize,
+}
+
+#[derive(Default)]
+struct TopCal {
+    top: TopThree,
+    curr_sum: usize,
+}
+
+impl TopCal {
+    const fn push_line(self, line: Option<usize>) -> Self {
+        match line {
+            Some(cal) => TopCal {
+                curr_sum: self.curr_sum + cal,
+                ..self
+            },
+            None => TopCal {
+                curr_sum: 0,
+                top: TopThree::push_sum(self.top, self.curr_sum),
+            },
+        }
+    }
+}
+
+impl TopThree {
+    const fn push_sum(self, sum: usize) -> Self {
+        let (first, second, third) = if sum > self.first {
+            (sum, self.first, self.second)
+        } else if sum > self.second {
+            (self.first, sum, self.second)
+        } else if sum > self.third {
+            (self.first, self.second, sum)
+        } else {
+            (self.first, self.second, self.third)
+        };
+        Self {
+            first,
+            second,
+            third,
+        }
+    }
+    const fn total_sum(&self) -> usize {
+        self.first + self.second + self.third
+    }
+}
+
+fn main() {
+    let file = ::std::env::args()
+        .skip(1)
+        .next()
+        .unwrap_or_else(|| String::from("./input"));
+    let file = BufReader::new(File::open(file).expect("Input file not found"));
+    let TopCal { top, .. } = file
+        .lines()
+        .map(Result::unwrap)
+        .map(either_calories_or_blank)
+        .collect();
+    println!(
+        "Max calories carried by a elves ({}, {}, {}): {}",
+        top.first,
+        top.second,
+        top.third,
+        top.total_sum()
+    );
+}
+
+impl FromIterator<Option<usize>> for TopCal {
+    fn from_iter<T: IntoIterator<Item = Option<usize>>>(iter: T) -> Self {
+        let max = iter.into_iter().fold(Self::default(), TopCal::push_line);
+        // Make sure to read one extra empty line at the end
+        TopCal::push_line(max, None)
+    }
+}

flake.lock

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+{
+  "nodes": {
+    "crane": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1661875961,
+        "narHash": "sha256-f1h/2c6Teeu1ofAHWzrS8TwBPcnN+EEu+z1sRVmMQTk=",
+        "owner": "ipetkov",
+        "repo": "crane",
+        "rev": "d9f394e4e20e97c2a60c3ad82c2b6ef99be19e24",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ipetkov",
+        "repo": "crane",
+        "type": "github"
+      }
+    },
+    "devshell": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1667210711,
+        "narHash": "sha256-IoErjXZAkzYWHEpQqwu/DeRNJGFdR7X2OGbkhMqMrpw=",
+        "owner": "numtide",
+        "repo": "devshell",
+        "rev": "96a9dd12b8a447840cc246e17a47b81a4268bba7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "devshell",
+        "type": "github"
+      }
+    },
+    "dream2nix": {
+      "inputs": {
+        "alejandra": [
+          "nixCargoIntegration"
+        ],
+        "all-cabal-json": [
+          "nixCargoIntegration"
+        ],
+        "crane": "crane",
+        "devshell": [
+          "nixCargoIntegration",
+          "devshell"
+        ],
+        "flake-parts": "flake-parts",
+        "flake-utils-pre-commit": [
+          "nixCargoIntegration"
+        ],
+        "ghc-utils": [
+          "nixCargoIntegration"
+        ],
+        "gomod2nix": [
+          "nixCargoIntegration"
+        ],
+        "mach-nix": [
+          "nixCargoIntegration"
+        ],
+        "nix-pypi-fetcher": "nix-pypi-fetcher",
+        "nixpkgs": [
+          "nixCargoIntegration",
+          "nixpkgs"
+        ],
+        "poetry2nix": [
+          "nixCargoIntegration"
+        ],
+        "pre-commit-hooks": [
+          "nixCargoIntegration"
+        ]
+      },
+      "locked": {
+        "lastModified": 1669743839,
+        "narHash": "sha256-zxnaRaWfCJxy0JlORD4Kmtzd0pfpcGLnyaCIJY8OlIo=",
+        "owner": "nix-community",
+        "repo": "dream2nix",
+        "rev": "b6af93946130748f72671dfd2ab84a5aeaf1f191",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "dream2nix",
+        "type": "github"
+      }
+    },
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": "nixpkgs-lib"
+      },
+      "locked": {
+        "lastModified": 1668450977,
+        "narHash": "sha256-cfLhMhnvXn6x1vPm+Jow3RiFAUSCw/l1utktCw5rVA4=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "d591857e9d7dd9ddbfba0ea02b43b927c3c0f1fa",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
+    "nix-pypi-fetcher": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1669065297,
+        "narHash": "sha256-UStjXjNIuIm7SzMOWvuYWIHBkPUKQ8Id63BMJjnIDoA=",
+        "owner": "DavHau",
+        "repo": "nix-pypi-fetcher",
+        "rev": "a9885ac6a091576b5195d547ac743d45a2a615ac",
+        "type": "github"
+      },
+      "original": {
+        "owner": "DavHau",
+        "repo": "nix-pypi-fetcher",
+        "type": "github"
+      }
+    },
+    "nixCargoIntegration": {
+      "inputs": {
+        "devshell": "devshell",
+        "dream2nix": "dream2nix",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      },
+      "locked": {
+        "lastModified": 1669788752,
+        "narHash": "sha256-2rFW93yI0oa78IMMa0PFk0h9oPo/GLzNTFOb9bb/yfo=",
+        "owner": "yusdacra",
+        "repo": "nix-cargo-integration",
+        "rev": "f65b42f7499e242f2af48153bb9baa621e9e45e6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "yusdacra",
+        "repo": "nix-cargo-integration",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1669542132,
+        "narHash": "sha256-DRlg++NJAwPh8io3ExBJdNW7Djs3plVI5jgYQ+iXAZQ=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "a115bb9bd56831941be3776c8a94005867f316a7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-lib": {
+      "locked": {
+        "dir": "lib",
+        "lastModified": 1665349835,
+        "narHash": "sha256-UK4urM3iN80UXQ7EaOappDzcisYIuEURFRoGQ/yPkug=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "34c5293a71ffdb2fe054eb5288adc1882c1eb0b1",
+        "type": "github"
+      },
+      "original": {
+        "dir": "lib",
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixCargoIntegration": "nixCargoIntegration"
+      }
+    },
+    "rust-overlay": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1669775522,
+        "narHash": "sha256-6xxGArBqssX38DdHpDoPcPvB/e79uXyQBwpBcaO/BwY=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "3158e47f6b85a288d12948aeb9a048e0ed4434d6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs = {
+    nixCargoIntegration.url = "github:yusdacra/nix-cargo-integration";
+  };
+
+  outputs = inputs:
+    inputs.nixCargoIntegration.lib.makeOutputs {
+      root = ./.;
+      config = common: {
+        shell = {
+          packages = with common.pkgs; [
+            rust-analyzer
+            lldb
+            treefmt
+            cargo-watch
+            cargo-flamegraph
+            pkg-config
+            hyperfine
+          ];
+        };
+      };
+    };
+}