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-rw-r--r--Sources/GraphAlgo.cpp109
1 files changed, 65 insertions, 44 deletions
diff --git a/Sources/GraphAlgo.cpp b/Sources/GraphAlgo.cpp
index 3fdd795..3da7c8d 100644
--- a/Sources/GraphAlgo.cpp
+++ b/Sources/GraphAlgo.cpp
@@ -4,62 +4,83 @@
#include <vector>
#include <algorithm>
+
+#include <iostream>
+#include <algorithm>
+#include <vector>
+#include <numeric>
+
using std::vector;
-//using std::pair;
+using std::pair;
+using namespace std;
+
+// https://stackoverflow.com/questions/1577475/c-sorting-and-keeping-track-of-indexes
+template <typename T>
+vector<size_t> sort_indexes(const vector<T>& v) {
-void explore(vector<vector<int>> &adj, int v, vector<int> &visited, vector<int> &prev,
- vector<int> &postv, vector<int> &clock) {
- visited.push_back(v);
- prev[v] = clock[0];
- clock[0] = clock[0] + 1;
+ // initialize original index locations
+ vector<size_t> idx(v.size());
+ iota(idx.begin(), idx.end(), 0);
- for (size_t i = 0; i < adj[v].size(); i++) {
- if (std::find(visited.begin(), visited.end(), adj[v][i])
- == visited.end())
- explore(adj, adj[v][i], visited, prev, postv, clock);
- }
- postv[v] = clock[0];
- clock[0] = clock[0] + 1;
+ // sort indexes based on comparing values in v
+ // using std::stable_sort instead of std::sort
+ // to avoid unnecessary index re-orderings
+ // when v contains elements of equal values
+ stable_sort(idx.begin(), idx.end(),
+ [&v](size_t i1, size_t i2) {return v[i1] > v[i2]; });
+ return idx;
}
-void dfs(vector<vector<int>> &adj, vector<int> &visited, vector<int> &prev,
- vector<int> &postv, vector<int> &clock) {
- for (size_t v = 0; v < adj.size(); v++) {
- if (std::find(visited.begin(), visited.end(), v) == visited.end())
- explore(adj, v, visited, prev, postv, clock);
- }
+void postVisit(int v, vector<int>& clock, vector<int>& postV) {
+ postV[v] = clock[0];
+ clock[0] = clock[0] + 1;
+}
+void explore(int v, vector<vector<int>> &adj, vector<bool>& visited, vector<int>& postV, vector<int>& clock) {
+ visited[v] = true;
+ for (int w : adj[v]) {
+ if (!visited[w])
+ explore(w, adj, visited, postV, clock);
+ }
+ postVisit(v, clock, postV);
}
-int acyclic(vector<vector<int> > &adj) {
- vector<int> visited;
- vector<int> prev(adj.size(), 0);
- vector<int> postv(adj.size(), 0);
- vector<int> clock(1, 0);
- dfs(adj, visited, prev, postv, clock);
+void dfs(vector<vector<int> >& adj, vector<bool>& visited, vector<int>& postV, vector<int>& clock) {
+ for (size_t v = 0; v < adj.size(); v++) {
+ if (!visited[v])
+ explore(v, adj, visited, postV, clock);
+ }
+}
- for (size_t u = 0; u < adj.size(); u++) {
- for (size_t i = 0; i < adj[u].size(); i++) {
- if (postv[u] <= postv[adj[u][i]])
- return 1;
- }
- }
- return 0;
+vector<int> toposort(vector<vector<int> > adj) {
+ vector<bool> visited(adj.size(), false);
+ vector<int> order;
+ vector<int> postV(adj.size(), 0);
+ vector<int> clock(1, 0);
+
+ dfs(adj, visited, postV, clock);
+ for (auto i : sort_indexes(postV)) {
+ order.push_back(i);
+ }
+ return order;
+}
+
+int main() {
+ size_t n, m;
+ std::cin >> n >> m;
+ vector<vector<int> > adj(n, vector<int>());
+ for (size_t i = 0; i < m; i++) {
+ int x, y;
+ std::cin >> x >> y;
+ adj[x - 1].push_back(y - 1);
+ }
+ vector<int> order = toposort(adj);
+ for (size_t i = 0; i < order.size(); i++) {
+ std::cout << order[i] + 1 << " ";
+ }
}
//TEST(Acyclicity, ac1) {
// vector<vector<int>> adj = { { 1 }, { 2 }, { 0 }, { 0 } };
// ASSERT_EQ(acyclic(adj), 1);
//}
-
-int main() {
- size_t n, m;
- std::cin >> n >> m;
- vector<vector<int> > adj(n, vector<int>());
- for (size_t i = 0; i < m; i++) {
- int x, y;
- std::cin >> x >> y;
- adj[x - 1].push_back(y - 1);
- }
- std::cout << acyclic(adj);
-}