69 lines
1.8 KiB
Rust
69 lines
1.8 KiB
Rust
// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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//! Vector extensions.
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/// Returns len of prefix shared with elem
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///
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/// ```rust
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/// extern crate ethcore_util as util;
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/// use util::vector::SharedPrefix;
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///
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/// fn main () {
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/// let a = vec![1,2,3,3,5];
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/// let b = vec![1,2,3];
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/// assert_eq!(a.shared_prefix_len(&b), 3);
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/// }
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/// ```
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pub trait SharedPrefix<T> {
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/// Get common prefix length
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fn shared_prefix_len(&self, elem: &[T]) -> usize;
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}
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impl<T> SharedPrefix<T> for [T] where T: Eq {
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fn shared_prefix_len(&self, elem: &[T]) -> usize {
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use std::cmp;
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let len = cmp::min(self.len(), elem.len());
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(0..len).take_while(|&i| self[i] == elem[i]).count()
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}
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}
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#[cfg(test)]
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mod test {
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use vector::SharedPrefix;
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#[test]
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fn test_shared_prefix() {
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let a = vec![1,2,3,4,5,6];
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let b = vec![4,2,3,4,5,6];
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assert_eq!(a.shared_prefix_len(&b), 0);
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}
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#[test]
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fn test_shared_prefix2() {
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let a = vec![1,2,3,3,5];
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let b = vec![1,2,3];
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assert_eq!(a.shared_prefix_len(&b), 3);
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}
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#[test]
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fn test_shared_prefix3() {
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let a = vec![1,2,3,4,5,6];
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let b = vec![1,2,3,4,5,6];
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assert_eq!(a.shared_prefix_len(&b), 6);
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}
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}
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