add bigraph-match

graph/bigraph-match.cc

@@ -0,0 +1,58 @@
+// uoj-78.cc
+
+#include<bits/stdc++.h>
+using namespace std;
+
+int main() {
+    ios_base::sync_with_stdio(0), cin.tie(NULL);
+    int nl, nr, m;
+    cin >> nl >> nr >> m;
+    vector<vector<int>> left(nl+1);
+    vector<vector<int>> right(nr+1);
+    vector<int> choice_left(nl+1);
+    vector<int> choice_right(nr+1);
+    vector<int> vis(nl+1);
+    while(m--) {
+        int v, u;
+        cin >> v >> u;
+        left[v].push_back(u);
+        right[u].push_back(v);
+    }
+    function<bool(int)> dfs = [&](int v) -> bool {
+        if (vis[v]) return false;
+        vis[v] = true;
+        for (auto&& u : left[v]) {
+            if (choice_right[u]) {
+                int t = choice_right[u];
+                if (dfs(t)) {
+                    choice_left[v] = u;
+                    choice_right[u] = v;
+                    vis[v] = false;
+                    return true;
+                }
+            } else {
+                choice_left[v] = u;
+                choice_right[u] = v;
+                vis[v] = false;
+                return true;
+            }
+        }
+        return false;
+    };
+    for (int i = 1; i <= nl; ++i) {
+        if (!choice_left[i]) {
+            dfs(i);
+        }
+    }
+    vector<int> res;
+    int cnt = 0;
+    for (int i = 1; i <= nl; ++i) {
+        if (choice_left[i]) {
+            ++cnt;
+        }
+        res.push_back(choice_left[i]);
+    }
+    cout << cnt << endl;
+    for (auto&& j : res)
+        cout << j << ' ';
+}