hihoCoder#1121 二分图一•二分图判定

原题地址

图的遍历，深度优先

向来对图的数据结构就练习的比较少，这种题目还是挺好的。

代码：

#include <iostream>
#include <vector>
#include <set>

using namespace std;

bool dye(vector<vector<int> > &graph, vector<int> &nodes, int i) {
  for (auto j : graph[i]) {
    if (nodes[j] == 0) {
      nodes[j] = -1 * nodes[i];
      if (!dye(graph, nodes, j))
        return false;
    }
    else if (nodes[j] == nodes[i])
      return false;
  }

  return true;
}

int main() {
  int T, N, M;

  cin >> T;
  while (T--) {
    cin >> N >> M;
    vector<vector<int> > graph(N, vector<int>());
    for (int i = 0; i < M; i++) {
      int a, b;
      cin >> a >> b;
      graph[a - 1].push_back(b - 1);
      graph[b - 1].push_back(a - 1);
    }

    vector<int> nodes(N, 0);
    bool ok = true;
    for (int i = 0; i < N; i++) {
      if (nodes[i] == 0 && !graph[i].empty()) {
        nodes[i] = 1;
        if (!dye(graph, nodes, i)) {
          ok = false;
          break;
        }
      }
    }
    cout << (ok ? "Correct" : "Wrong") << endl;
  }
  return 0;
}