36 lines
911 B
Rust
36 lines
911 B
Rust
use std::{
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fs::File,
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io::{BufReader, Read}, collections::HashSet,
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};
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fn main() -> () {
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let input = File::open("input.txt").unwrap();
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let buf = BufReader::new(input);
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let window_size = 4;
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let mut chars_iter = buf.bytes();
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let mut window = vec![0u8; 4];
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let mut dup_check = HashSet::<u8>::with_capacity(4);
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let mut cursor = window_size - 1;
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// initialise buffer
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for i in 0..window_size - 1 {
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window[i] = chars_iter.next().unwrap().unwrap();
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}
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// find non-duplicate window
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let pos = chars_iter.position(|byte| {
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let byte = byte.unwrap();
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window[cursor] = byte;
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cursor = (cursor + 1) % window_size;
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dup_check.clear();
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dup_check.extend(window.iter());
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dup_check.len() == window_size
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}).unwrap();
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let pos = pos + window_size; // account for buffer initialisation
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println!("{}", pos);
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}
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