def yosupo_bi_match() -> None:
# https://judge.yosupo.jp/problem/bipartitematching
import scipy
major, minor, _ = map(int, scipy.version.full_version.split('.'))
if major < 1 or (major == 1 and minor < 4):
raise RuntimeError
L, R, M = map(int, input().split())
sink, source = L + R, L + R + 1
in_, out = [], []
edges = []
for _ in range(M):
a, b = map(int, input().split())
in_.append(a)
out.append(b + L)
edges.append((a, b + L))
for i in range(L):
in_.append(source)
out.append(i)
edges.append((i, source))
for i in range(R):
in_.append(i + L)
out.append(sink)
edges.append((i + L, sink))
edges.sort()
graph = csr_matrix((np.ones(L + R + M, dtype=int), (in_, out)),
shape=(L + R + M, L + R + M))
flow = maximum_flow(graph, source, sink)
ans = []
for (fr, to), val in zip(edges, flow.residual.data):
if 0 <= fr < L and L <= to < L + R and val == 1:
ans.append((fr, to - L))
print(flow.flow_value)
print("\n".join(f"{v1} {v2}" for v1, v2 in ans))
def test_ford_fulkerson():
"""
最大ノード数 M, 最大重み M, 最大辺数ノード数 * 2 で重み付き逆平行有向グラフをランダム作成することを Iteration 回行う。
それぞれに対し、ソースとシンクを選んでフローを流すことをノード数だけ行い、scipy.sparse.csgraph.maximum_flow と結果を照合するストレステストを行う。
"""
Iteration = 20
M = 20
for _ in range(Iteration):
n = randint(2, M)
# ---- ndarray, csr_matrix, エッジを張った FordFulkerson インスタンス生成 ----
mat = np.full((n, n), 0)
for _ in range(2 * n): # 最大で 2 * n 個辺を張る
a, b = randint(0, n - 1), randint(0, n - 1)
if a == b: # 自己ループはだめ
continue
if mat[b, a] == 0: # 逆平行有向グラフにしたいので
mat[a, b] = randint(1, M) # 上書きすることも多々あるだろう
G = csr_matrix(mat)
FF = FordFulkerson(n)
for i in range(n):
for j in range(n):
if mat[i, j] != 0:
assert i != j
assert mat[j, i] == 0
FF.add_edge(i, j, mat[i, j])
# ---- source, sink を決定しフローを流して比較 ----
for i in range(n):
while True:
source, sink = randint(0, n - 1), randint(0, n - 1)
if source != sink:
break
# ford_fulkerson をチェック
if i % 2 == 0:
expected_max_flow = cs.maximum_flow(G, source, sink).flow_value
state = FF.reserve_state()
got_max_flow = FF.ford_fulkerson(source, sink)
assert got_max_flow == expected_max_flow
FF.restore_state(state)
# edmonds_karp をチェック
else:
expected_max_flow = cs.maximum_flow(G, source, sink).flow_value
state = FF.reserve_state()
got_max_flow = FF.edmonds_karp(source, sink)
assert got_max_flow == expected_max_flow
FF.restore_state(state)
def find_flow_and_split(top_level_indices, graph_rep_array, n_1, n_2,
classifier_probs):
sink_idx = n_1 + n_2 + 1
top_level_indices_1 = None
top_level_indices_2 = None
#Create subgraph from index array provided
graph_rep_curr = graph_rep_array[top_level_indices]
graph_rep_curr = graph_rep_curr[:, top_level_indices]
graph_rep_curr, n_1_curr, n_2_curr = graph_rescale(graph_rep_curr,
top_level_indices, n_1,
n_2)
graph_curr = csr_matrix(graph_rep_curr)
flow_curr = maximum_flow(graph_curr, 0, len(top_level_indices) - 1)
# Checking if full flow occurred, so no need to split
if flow_curr.flow_value == n_1_curr * n_2_curr:
set_classifier_prob_full_flow(top_level_indices, n_1_curr, n_2_curr,
sink_idx, classifier_probs)
return top_level_indices_1, top_level_indices_2, flow_curr
elif flow_curr.flow_value == 0:
set_classifier_prob_no_flow(top_level_indices, sink_idx, n_1,
classifier_probs)
return top_level_indices_1, top_level_indices_2, flow_curr
# Finding remaining capacity edges
remainder_array = graph_curr - flow_curr.residual
rev_edge_ptr, tails = _make_edge_pointers(remainder_array)
edge_ptr = remainder_array.indptr
capacities = remainder_array.data
heads = remainder_array.indices
edge_list_curr = find_remaining_cap_edges(edge_ptr, capacities, heads,
tails, 0,
len(top_level_indices) - 1)
# print(edge_list_curr)
gz_idx = []
for item in edge_list_curr:
gz_idx.append(item[0])
gz_idx.append(item[1])
if len(gz_idx) > 0:
gz_idx = np.array(gz_idx)
gz_idx_unique = np.unique(gz_idx)
top_level_gz_idx = top_level_indices[gz_idx_unique]
top_level_gz_idx = np.insert(top_level_gz_idx, len(top_level_gz_idx),
sink_idx)
top_level_indices_1 = top_level_gz_idx
else:
top_level_gz_idx = np.array([0, sink_idx])
# Indices without flow
top_level_z_idx = np.setdiff1d(top_level_indices, top_level_gz_idx)
if len(top_level_z_idx) > 0:
# Add source and sink back to zero flow idx array
top_level_z_idx = np.insert(top_level_z_idx, 0, 0)
top_level_z_idx = np.insert(top_level_z_idx, len(top_level_z_idx),
sink_idx)
top_level_indices_2 = top_level_z_idx
return top_level_indices_1, top_level_indices_2, flow_curr
def test_simple_graph(method):
# This graph looks as follows:
# (0) --5--> (1)
graph = csr_matrix([[0, 5], [0, 0]])
res = maximum_flow(graph, 0, 1, method=method)
assert res.flow_value == 5
expected_flow = np.array([[0, 5], [-5, 0]])
assert_array_equal(res.flow.toarray(), expected_flow)
def test_simple_graph(dfs):
# This graph looks as follows:
# (0) --5--> (1)
graph = csr_matrix([[0, 5], [0, 0]])
res = maximum_flow(graph, 0, 1, dfs=dfs)
assert res.flow_value == 5
expected_residual = np.array([[0, 5], [-5, 0]])
assert_array_equal(res.residual.toarray(), expected_residual)
def test_bottle_neck_graph(method):
# This graph cannot use the full capacity between 0 and 1:
# (0) --5--> (1) --3--> (2)
graph = csr_matrix([[0, 5, 0], [0, 0, 3], [0, 0, 0]])
res = maximum_flow(graph, 0, 2, method=method)
assert res.flow_value == 3
expected_flow = np.array([[0, 3, 0], [-3, 0, 3], [0, -3, 0]])
assert_array_equal(res.flow.toarray(), expected_flow)
def _part_two(data):
"""
Once again solve a matching problem with
maxflow
"""
c = _parse_allergens(data)
allergens = sorted(c.keys())
ingredients = set()
for r in c.values():
ingredients.update(r)
ingredients = list(ingredients)
print(allergens)
print(ingredients)
assert len(ingredients) == len(allergens)
N = 1 + len(ingredients) + len(allergens) + 1
def a_index(a):
return 1 + a
def i_index(i):
return 1 + len(allergens) + i
C = np.zeros([N, N], dtype=int)
src = 0
snk = N - 1
for a, alg in enumerate(allergens):
C[src, a_index(a)] = 1 # src to left side
print(a, alg, c[alg])
for ing in c[alg]:
i = ingredients.index(ing)
C[a_index(a), i_index(i)] = 1
for i in range(len(ingredients)):
C[i_index(i), snk] = 1 # rhs to sink
print(C)
result = maximum_flow(csr_matrix(C), src, snk)
assert result.flow_value == len(ingredients), result
print(f"flow_value: {result.flow_value}")
answer = []
for a, alg in enumerate(allergens):
for ing in c[alg]:
i = ingredients.index(ing)
if result.residual[a_index(a), i_index(i)] == 1:
answer.append(ing)
break
return ','.join(answer)
def test_disconnected_graph(method):
# This tests the following disconnected graph:
# (0) --5--> (1) (2) --3--> (3)
graph = csr_matrix([[0, 5, 0, 0], [0, 0, 0, 0], [0, 0, 9, 3], [0, 0, 0,
0]])
res = maximum_flow(graph, 0, 3, method=method)
assert res.flow_value == 0
expected_flow = np.zeros((4, 4), dtype=np.int32)
assert_array_equal(res.flow.toarray(), expected_flow)
def test_add_reverse_edges_large_graph(method):
# Regression test for https://github.com/scipy/scipy/issues/14385
n = 100_000
indices = np.arange(1, n)
indptr = np.array(list(range(n)) + [n - 1])
data = np.ones(n - 1, dtype=np.int32)
graph = csr_matrix((data, indices, indptr), shape=(n, n))
res = maximum_flow(graph, 0, n - 1, method=method)
assert res.flow_value == 1
expected_flow = graph - graph.transpose()
assert_array_equal(res.flow.data, expected_flow.data)
assert_array_equal(res.flow.indices, expected_flow.indices)
assert_array_equal(res.flow.indptr, expected_flow.indptr)
def test_example_from_clrs_chapter_26_1(method):
# See page 659 in CLRS second edition, but note that the maximum flow
# we find is slightly different than the one in CLRS; we push a flow of
# 12 to v_1 instead of v_2.
graph = csr_matrix([[0, 16, 13, 0, 0, 0], [0, 0, 10, 12, 0, 0],
[0, 4, 0, 0, 14, 0], [0, 0, 9, 0, 0, 20],
[0, 0, 0, 7, 0, 4], [0, 0, 0, 0, 0, 0]])
res = maximum_flow(graph, 0, 5, method=method)
assert res.flow_value == 23
expected_flow = np.array([[0, 12, 11, 0, 0, 0], [-12, 0, 0, 12, 0, 0],
[-11, 0, 0, 0, 11, 0], [0, -12, 0, 0, -7, 19],
[0, 0, -11, 7, 0, 4], [0, 0, 0, -19, -4, 0]])
assert_array_equal(res.flow.toarray(), expected_flow)
def solve_for_row_and_column_sums(row_sums, col_sums):
"""
applies the max flow algorithm for matrix rounding
"""
m = len(row_sums)
n = len(col_sums)
# produce a sparse matrix object and solve
graph = csr_matrix(prod_target_matrix(row_sums, col_sums))
solution = maximum_flow(graph, 0, m+n+1).residual.toarray()[1:(m+1), (m+1):(m+n+1)]
return solution
def scipy_maxflow(G: nx.DiGraph, s, t, capacity='capacity', **kwargs):
cap = nx.get_edge_attributes(G, capacity)
edges = G.edges
cap = [cap[e] for e in edges]
edges = np.array(edges)
sparse_G = csr_matrix((cap, (edges[:, 0], edges[:, 1])),
shape=(edges.max() + 1, ) * 2)
res = csgraph.maximum_flow(sparse_G, s, t)
R = nx.algorithms.flow.utils.build_residual_network(G, 'capacity')
R.graph['flow_value'] = res.flow_value
residual = res.residual
for i, j in R.edges:
R[i][j]['flow'] = residual[i, j]
return R
def test_backwards_flow(method):
# This example causes backwards flow between vertices 3 and 4,
# and so this test ensures that we handle that accordingly. See
# https://stackoverflow.com/q/38843963/5085211
# for more information.
graph = csr_matrix([[0, 10, 0, 0, 10, 0, 0, 0], [0, 0, 10, 0, 0, 0, 0, 0],
[0, 0, 0, 10, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 10],
[0, 0, 0, 10, 0, 10, 0, 0], [0, 0, 0, 0, 0, 0, 10, 0],
[0, 0, 0, 0, 0, 0, 0, 10], [0, 0, 0, 0, 0, 0, 0, 0]])
res = maximum_flow(graph, 0, 7, method=method)
assert res.flow_value == 20
expected_flow = np.array([[0, 10, 0, 0, 10, 0, 0, 0],
[-10, 0, 10, 0, 0, 0, 0, 0],
[0, -10, 0, 10, 0, 0, 0, 0],
[0, 0, -10, 0, 0, 0, 0, 10],
[-10, 0, 0, 0, 0, 10, 0, 0],
[0, 0, 0, 0, -10, 0, 10, 0],
[0, 0, 0, 0, 0, -10, 0, 10],
[0, 0, 0, -10, 0, 0, -10, 0]])
assert_array_equal(res.flow.toarray(), expected_flow)
def reduction_implication_network(self, rounding_parameter):
"""
Use an implication network to reduce the current problem instance.
:param rounding_parameter: the projection data will be truncated to [rounding_parameter], in order to be able
to use integer capacities in the implication network.
"""
current_N = self.A.shape[1]
A_csc = self.A.tocsc()
B = 10**rounding_parameter * A_csc.transpose() * A_csc
int_y = (10**rounding_parameter * self.y +
0.1 * np.ones_like(self.y)).astype(int)
diagonal = B.diagonal()
B -= csr_matrix(np.diag(diagonal))
A_y = self.A.transpose() @ int_y
outeredges = csr_matrix(2 * A_y - diagonal)
Adjacency_matrix = 2 * sparse.bmat(
[[None, 2 * B, None, None],
[None, None, None, outeredges.transpose()],
[outeredges, None, None, None], [None, None, 0, None]],
format='csr')
max_flow_output = csgraph.maximum_flow(Adjacency_matrix, 2 * current_N,
2 * current_N + 1)
flow = max_flow_output.residual
symmetric_central_flow = flow[:current_N, current_N:2 *
current_N] + flow[:current_N,
current_N:2 *
current_N].transpose()
symmetric_central_flow.data //= 2
flow[:current_N, current_N:2 * current_N] = symmetric_central_flow
flow[current_N:2 * current_N, :current_N] = -symmetric_central_flow
symmetric_outer_flow = \
flow[2*current_N, :current_N] + flow[current_N: 2 * current_N, 2*current_N + 1].transpose()
symmetric_outer_flow.data //= 2
flow[2 * current_N, :current_N] = symmetric_outer_flow
flow[current_N:2 * current_N,
2 * current_N + 1] = symmetric_outer_flow.transpose()
residual = Adjacency_matrix - flow
residual.eliminate_zeros()
n_components, labels = csgraph.connected_components(
residual, connection='strong')
component_type = np.zeros(n_components, dtype=int)
# Type 14: u and 1 - u are both contained in the component
# Type 15: u is contained in the component, 1 - u is not, no path from u to u - 1
# Type 16: u is contained in the component, 1 - u is not, there exists a path from u to u - 1
indices = []
vals = []
for i in range(current_N):
component = labels[i]
if component_type[component] == 0:
if component == labels[i + current_N]:
component_type[component] = 14
else:
reachable = csgraph.breadth_first_order(
residual, i, return_predecessors=False)
if i + current_N in reachable:
component_type[component] = 16
else:
component_type[component] = 15
if component_type[component] == 15:
indices.append(i)
vals.append(1)
elif component_type[component] == 16:
indices.append(i)
vals.append(0)
no_reductions = len(indices)
order = np.array(indices).argsort()
for j in range(no_reductions):
i = order[no_reductions - j - 1]
self.problem_reduction_single(indices[i], vals[i])
return 0
def test_raises_when_sink_is_out_of_bounds(sink, method):
with pytest.raises(ValueError):
graph = csr_matrix([[0, 1], [0, 0]])
maximum_flow(graph, 0, sink, method=method)
def test_raises_when_source_is_sink():
with pytest.raises(ValueError):
graph = csr_matrix([[0, 1], [0, 0]])
maximum_flow(graph, 0, 0)
maximum_flow(graph, 0, 0, method='edmonds_karp')
def test_raises_on_non_square_input():
with pytest.raises(ValueError):
graph = csr_matrix([[0, 1, 2], [2, 1, 0]])
maximum_flow(graph, 0, 1)
def test_raises_on_floating_point_input():
with pytest.raises(ValueError):
graph = csr_matrix([[0, 1.5], [0, 0]], dtype=np.float64)
maximum_flow(graph, 0, 1)
maximum_flow(graph, 0, 1, method='edmonds_karp')
def test_raises_on_csc_input():
with pytest.raises(TypeError):
graph = csc_matrix([[0, 1], [0, 0]])
maximum_flow(graph, 0, 1)
maximum_flow(graph, 0, 1, method='edmonds_karp')
def test_residual_raises_deprecation_warning():
graph = csr_matrix([[0, 5, 0], [0, 0, 3], [0, 0, 0]])
res = maximum_flow(graph, 0, 2)
with pytest.deprecated_call():
res.residual
from scipy.sparse import csr_matrix
from scipy.sparse.csgraph import maximum_flow
import numpy as np
inf = 100000000
n = int(input())
l = list(map(int , input().split())) # plus one is the index
e = int(input())
m = [[0 for i in range(n+1)] for i in range(n+1)]
for i in range(e):
q1 , q2 , c = tuple(map(int ,input().split()))
m[q1][q2] = c
for i in range(n):
if l[i]==1:
m[0][i+1]=inf
graph = csr_matrix(m)
print(maximum_flow(graph, 0, l.index(2)+1).flow_value)
##connect all source with one source before them with edge capacity of infinte
#index zero is the base source
#source : 1 , node : 0 , sink : 2
def _get_valid_rules(rules, tickets) -> Dict[str, int]:
# Let's try this using maxflow
R = len(rules)
T = len(tickets)
# F is just number of rules
F = R
N = 1 + R + F + 1
C = np.zeros((N, N), dtype=int)
# Initialize arcs from source to tickets
src = 0
snk = N - 1
def rule_index(r):
return 1 + r
def field_index(f):
return 1 + R + f
# source to rule
for r in range(R):
C[src, rule_index(r)] = 1
# fields to snk
for f in range(F):
C[field_index(f), snk] = 1
# rules
for r in range(R):
for f in range(F):
valid = all(rules[r].is_valid(t[f]) for t in tickets)
if not valid:
continue
C[rule_index(r), field_index(f)] = 1
print(f"dims: T: {T}, F: {F}, R: {R}, N: {N}")
print(C)
print("Converting to CSR...")
C = csr_matrix(C)
print(f"Solving max flow for matrix shape {C.shape}...")
result = maximum_flow(C, src, snk)
print(f"result: {result.flow_value}")
if (result.flow_value != R):
print(f"Uh oh, not enough flow!")
residual = result.residual
matches = dict()
for r in range(R):
for f in range(F):
try:
if residual[rule_index(r), field_index(f)] == 1:
rule = rules[r]
if rule.name in matches:
raise ValueError()
matches[rule.name] = f
except KeyError:
continue
if not set(range(F)) == set(matches.values()):
print("Error: Invalid matching!")
return matches
def test_raises_when_source_is_out_of_bounds(source):
with pytest.raises(ValueError):
graph = csr_matrix([[0, 1], [0, 0]])
maximum_flow(graph, source, 1)
def time_maximum_flow(self, n, density):
maximum_flow(self.data, 0, n - 1)
def test_raises_on_dense_input():
with pytest.raises(TypeError):
graph = np.array([[0, 1], [0, 0]])
maximum_flow(graph, 0, 1)
maximum_flow(graph, 0, 1, method='edmonds_karp')
def min_cut(self): self.graph = csr_matrix((self.weight, (self.from_node, self.to_node)), shape=(self.N+2, self.N+2)) max_flow = maximum_flow(self.graph, self.bgd_src, self.fgd_sink) return max_flow
from scipy.sparse import csr_matrix
from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError, maximum_bipartite_matching, maximum_flow, minimum_spanning_tree
import numpy as np
n, m = map(int, input().split())
edges = [list(map(int, input().split())) for i in range(m)]
def graph_csr(edges, n, directed=True, indexed_1=True): # 隣接リストから粗行列を作成
arr = np.array(edges, dtype=np.int64).T
arr = arr.astype(np.int64)
index = int(indexed_1)
if not directed:
return csr_matrix((np.concatenate([arr[2], arr[2]]), (np.concatenate([arr[0]-index, arr[1]-index]), np.concatenate([arr[1]-index, arr[0]-index]))), shape=(n, n))
else:
return csr_matrix((arr[2], (arr[0]-index, arr[1]-index)), shape=(n, n))
csr = graph_csr(edges, n)
try:
print(floyd_warshall(csr))
except NegativeCycleError:
print('-1')
dijkstra(csr, indices=0)
bellman_ford(csr, indices=0)
maximum_bipartite_matching(csr, perm_type='column')
maximum_flow(csr, source=0, sink=1).flow_value
maximum_flow(csr, source=0, sink=1).residual
int(sum(minimum_spanning_tree(csr).data))
