860. 染色法判定二分图

https://www.acwing.com/problem/content/submission/code_detail/36295038/

AcWing/860/860.cpp

@@ -0,0 +1,59 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, m;
+std::vector<int> g[N];
+int color[N];
+
+bool dfs(int u, int c) {
+    color[u] = c;
+
+    for (int v : g[u]) {
+        if (~color[v]) {                      // 如果已经染色
+            if (color[v] == c) return false;  // 同色，矛盾
+        } else {
+            if (!dfs(v, c ^ 1)) return false;
+        }
+    }
+
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    std::fill(std::begin(color), std::end(color), -1);
+
+    cin >> n >> m;
+
+    for (int i = 1, u, v; i <= m; i++) {
+        cin >> u >> v;
+
+        g[u].push_back(v);
+        g[v].push_back(u);
+    }
+
+    // 图可能不连通
+    for (int i = 1; i <= n; i++) {
+        if (!~color[i]) {  // 如果没有染色
+            if (!dfs(i, 0)) {
+                cout << "No" << endl;
+
+                exit(0);
+            }
+        }
+    }
+
+    cout << "Yes" << endl;
+
+    return 0;
+}