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Update graph/tarjan.cc 

Signed-off-by: subcrip <contact@subc.rip>
This commit is contained in:
subcrip 2024-05-11 18:39:31 +08:00
parent 1ac86aa595
commit cdc14e0060
1 changed files with 41 additions and 1 deletions
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graph/tarjan.cc
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@ -1,4 +1,14 @@
namespace tarjan {
struct mutex_cond {
int v1; bool cond1;
int v2; bool cond2;
mutex_cond(int v1, bool cond1, int v2, bool cond2) : v1(v1), cond1(cond1), v2(v2), cond2(cond2) {}
};
struct inclusive_cond {
int v1; bool cond1;
int v2; bool cond2;
inclusive_cond(int v1, bool cond1, int v2, bool cond2) : v1(v1), cond1(cond1), v2(v2), cond2(cond2) {}
};
// Returns the mapping between vertices and their affiliated sccs.
vector<int> scc(const vector<vector<int>>& ch) {
int n = ch.size();
@ -25,7 +35,6 @@ namespace tarjan {
}
return br;
}
// This method can eliminate redundant edges or self-loops
vector<vector<int>> build_scc(const vector<vector<int>>& ch) {
int n = ch.size();
@ -65,4 +74,35 @@ namespace tarjan {
}
return res;
}
// indices start from 1, result has `n` items
optional<vector<bool>> solve_twosat(int n, const vector<mutex_cond>& conditions) {
vector<vector<int>> ch(2 * n + 1);
for (auto&& [v1, cond1, v2, cond2] : conditions) {
ch[(1 ^ cond1) * n + v1].emplace_back(cond2 * n + v2);
ch[(1 ^ cond2) * n + v2].emplace_back(cond1 * n + v1);
}
auto sccno = scc(ch);
for (int i = 1; i <= n; ++i) {
if (sccno[i] == sccno[i + n]) {
return nullopt;
}
}
vector<bool> res;
for (int i = 1; i <= n; ++i) {
if (sccno[i] < sccno[i + n]) {
res.emplace_back(false);
} else {
res.emplace_back(true);
}
}
return res;
};
// indices start from 1, result has `n` items
optional<vector<bool>> solve_twosat(int n, const vector<inclusive_cond>& conditions) {
vector<mutex_cond> trans_conds;
for (auto&& [v1, cond1, v2, cond2] : conditions) {
trans_conds.emplace_back(v1, cond1, v2, not cond2);
}
return solve_twosat(n, trans_conds);
}
}