day9

day9/Cargo.toml

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+[package]
+name = "day9"
+version = "0.1.0"
+authors = ["henine"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day9/src/main.rs

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+use std::collections::VecDeque;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::cmp::{min, max};
+
+fn main() {
+    let file = match File::open("input") {
+        Ok(file) => file,
+        Err(e) => panic!(e)
+    };
+
+    let input_buffer = BufReader::new(&file);
+    let mut lines = input_buffer.lines();
+
+    let mut buffer = VecDeque::with_capacity(25);
+    let mut list = Vec::new();
+
+    for _i in 0..25 {
+        let input = lines.next().unwrap().unwrap().parse::<u32>().unwrap();
+        buffer.push_back(input);
+        list.push(input);
+    }
+
+    let mut code = 0;
+
+    for line in lines {
+        let input = line.unwrap().parse::<u32>().unwrap();
+
+        if !is_sum(&buffer, input) {
+            println!("Code: {}", input);
+            code = input;
+            break;
+        }
+
+        buffer.push_back(input);
+        buffer.pop_front();
+        list.push(input);
+    }
+
+    let mut start = 0;
+    let mut end = 1;
+    let mut sum = list[start] + list[end];
+
+    loop {
+        if sum == code {
+            println!("Sum: {}",
+                   list[start..end + 1].iter().fold(0, |x,y| max(x,*y)) +
+                       list[start..end + 1].iter().fold(list[start], |x,y|min(x,*y)));
+            break;
+        } else if sum > code {
+            sum -= list[start];
+            start += 1;
+        } else {
+            end += 1;
+            sum += list[end];
+        }
+    }
+}
+
+fn is_sum(buffer: &VecDeque<u32>, input: u32) -> bool {
+    for i in 0..buffer.len() - 1 {
+        for j in 1..buffer.len() {
+            if buffer[i] + buffer[j] == input {
+                return true;
+            }
+        }
+    }
+
+    false
+}

day9/test

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+35
+20
+15
+25
+47
+40
+62
+55
+65
+95
+102
+117
+150
+182
+127
+219
+299
+277
+309
+576