cp_library/alg/iter/slice_iterator_reverse_cls.py

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• Last update: 2025-03-30 20:17:47+09:00

Required by

• cp_library/alg/graph/fast/digraph_cls.py
• cp_library/alg/graph/fast/snippets/biconnected_components_vertices_fn.py
• cp_library/alg/graph/fast/snippets/strongly_connected_components_fn.py
• cp_library/alg/graph/fast/snippets/two_edge_connected_components_fn.py
• cp_library/alg/graph/strongly_connected_components_fn.py

Verified with

• test/atcoder/abc/abc218_f_fast_shortest_path.test.py
• test/library-checker/graph/biconnected_components.test.py
• test/library-checker/graph/cycle_detection.test.py
• test/library-checker/graph/scc.test.py
• test/library-checker/graph/scc_strongly_connected_components.test.py
• test/library-checker/graph/two_edge_connected_components.test.py

Code

import cp_library.alg.iter.__header__
from typing import Iterator, SupportsIndex
from cp_library.misc.typing import _T

class SliceIteratorReverse(Iterator[_T]):
    def __init__(self, A: list[_T], L: list[SupportsIndex]):
        self.A, self.L, self.r = A, L, len(A)
    def __len__(self): return len(self.L)
    def __next__(self):
        L = self.L
        if not L: raise StopIteration
        self.r, r = (l := L.pop()), self.r
        return self.A[l:r]

'''
╺━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━╸
             https://kobejean.github.io/cp-library               
'''
from typing import Iterator, SupportsIndex
from typing import TypeVar
_T = TypeVar('T')

class SliceIteratorReverse(Iterator[_T]):
    def __init__(self, A: list[_T], L: list[SupportsIndex]):
        self.A, self.L, self.r = A, L, len(A)
    def __len__(self): return len(self.L)
    def __next__(self):
        L = self.L
        if not L: raise StopIteration
        self.r, r = (l := L.pop()), self.r
        return self.A[l:r]

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