2018/02

2018/02/src/main.rs

@@ -0,0 +1,60 @@
+use std::collections::HashMap;
+use std::io::{self, BufRead};
+
+fn diff(left: &str, right: &str) -> Vec<(usize, (char, char))> {
+    left.chars()
+        .zip(right.chars())
+        .enumerate()
+        .filter(|(_, (a, b))| a != b)
+        .collect::<Vec<_>>()
+}
+
+fn main() {
+    let stdin = io::stdin();
+
+    let lines = stdin
+        .lock()
+        .lines()
+        .filter_map(Result::ok)
+        .map(|line| {
+            let mut map = HashMap::new();
+
+            for ch in line.chars() {
+                map.entry(ch).and_modify(|x| *x += 1).or_insert(1);
+            }
+
+            (line, map)
+        }).collect::<Vec<_>>();
+
+    let two = lines
+        .iter()
+        .filter(|(_, map)| map.iter().any(|(_, count)| *count == 2))
+        .count();
+    let three = lines
+        .iter()
+        .filter(|(_, map)| map.iter().any(|(_, count)| *count == 3))
+        .count();
+
+    println!("part.one={}", two * three);
+
+    for (i, (left, _)) in lines.iter().enumerate() {
+        let diff = lines
+            .iter()
+            .skip(i + 1)
+            .map(|(right, _)| diff(left, right))
+            .find(|diff| diff.len() == 1)
+            .map(|mut diff| diff.pop().unwrap());
+
+        if let Some((n, _)) = diff {
+            let string = left
+                .chars()
+                .enumerate()
+                .filter(|(i, _)| *i != n)
+                .map(|(_, c)| c)
+                .collect::<String>();
+
+            println!("part.two={:?}", string);
+            break;
+        }
+    }
+}