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Update graph/tarjan.cc 

Signed-off-by: subcrip <contact@subc.rip>
This commit is contained in:
subcrip 2024-04-16 18:41:34 +08:00
parent 760acb15f7
commit ab39eb6ea8
1 changed files with 6 additions and 2 deletions
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8
graph/tarjan.cc
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@ -1,4 +1,5 @@
namespace tarjan { namespace tarjan {
// Returns the mapping between vertices and their affiliated sccs.
vector<int> scc(const vector<vector<int>>& ch) { vector<int> scc(const vector<vector<int>>& ch) {
int n = ch.size(); int n = ch.size();
int cnt = 0, scn = 0; int cnt = 0, scn = 0;
@ -25,6 +26,7 @@ namespace tarjan {
return br; return br;
} }
// This method can eliminate redundant edges or self-loops
vector<vector<int>> build_scc(const vector<vector<int>>& ch) { vector<vector<int>> build_scc(const vector<vector<int>>& ch) {
int n = ch.size(); int n = ch.size();
auto br = scc(ch); auto br = scc(ch);
@ -32,7 +34,7 @@ namespace tarjan {
vector<unordered_set<int, safe_hash>> rb(cnt + 1); vector<unordered_set<int, safe_hash>> rb(cnt + 1);
for (int i = 0; i < n; ++i) { for (int i = 0; i < n; ++i) {
for (auto&& u : ch[i]) { for (auto&& u : ch[i]) {
rb[br[i]].emplace(br[u]); if (br[i] != br[u]) rb[br[i]].emplace(br[u]);
} }
} }
vector<vector<int>> res(cnt + 1); vector<vector<int>> res(cnt + 1);
@ -42,6 +44,8 @@ namespace tarjan {
return res; return res;
} }
// This method can eliminate redundant edges or self-loops
// return form: (scc size, children of scc)
vector<pair<size_t, vector<int>>> build_scc_with_size(const vector<vector<int>>& ch) { vector<pair<size_t, vector<int>>> build_scc_with_size(const vector<vector<int>>& ch) {
int n = ch.size(); int n = ch.size();
auto br = scc(ch); auto br = scc(ch);
@ -49,7 +53,7 @@ namespace tarjan {
vector<unordered_set<int, safe_hash>> rb(cnt + 1); vector<unordered_set<int, safe_hash>> rb(cnt + 1);
for (int i = 0; i < n; ++i) { for (int i = 0; i < n; ++i) {
for (auto&& u : ch[i]) { for (auto&& u : ch[i]) {
rb[br[i]].emplace(br[u]); if (br[i] != br[u]) rb[br[i]].emplace(br[u]);
} }
} }
vector<pair<size_t, vector<int>>> res(cnt + 1); vector<pair<size_t, vector<int>>> res(cnt + 1);