染色法判定二分图
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2021-02-04 21:43:01
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/* 染色法判定二分图 */
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 200010;
int n, m;
int h[N], e[N], ne[N], idx;
int color[N];
void add(int a, int b) {
e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}
bool dfs(int u, int c) {
color[u] = c;
for (int i = h[u]; i != -1; i = ne[i]) {
int j = e[i];
if (!color[j]) {
if (!dfs(j, 3 - c)) return false;
} else if (color[j] == c) {
return false;
}
}
return true;
}
int main() {
memset(h, -1, sizeof(h));
cin >> n >> m;
for (int i = 0; i < m; i++) {
int a, b;
cin >> a >> b;
add(a, b), add(b, a);
}
bool flag = true;
for (int i = 1; i <= n; i++) {
if (!color[i]) {
if (!dfs(i, 1)) {
flag = false;
break;
}
}
}
if (flag) puts("Yes");
else puts("No");
return 0;
}