## POJ 3207 Ikki’s Story IV – Panda’s Trick（2-sat）

2018年10月11日 ⁄ 综合 ⁄ 共 1390字 ⁄ 字号 评论关闭

# POJ 3207 Ikki's Story IV - Panda's Trick

```#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

const int MAXNODE = 2005;

struct TwoSet {
int n;
vector<int> g[MAXNODE * 2];
bool mark[MAXNODE * 2];
int S[MAXNODE * 2], sn;

void init(int tot) {
n = tot * 2;
for (int i = 0; i < n; i += 2) {
g[i].clear();
g[i^1].clear();
}
memset(mark, false, sizeof(mark));
}

void add_Edge(int u, int uval, int v, int vval) {
u = u * 2 + uval;
v = v * 2 + vval;
g[u^1].push_back(v);
g[v^1].push_back(u);
}

void delete_Edge(int u, int uval, int v, int vval) {
u = u * 2 + uval;
v = v * 2 + vval;
g[u^1].pop_back();
g[v^1].pop_back();
}

bool dfs(int u) {
if (mark[u^1]) return false;
if (mark[u]) return true;
mark[u] = true;
S[sn++] = u;
for (int i = 0; i < g[u].size(); i++) {
int v = g[u][i];
if (!dfs(v)) return false;
}
return true;
}

bool solve() {
for (int i = 0; i < n; i += 2) {
if (!mark[i] && !mark[i + 1]) {
sn = 0;
if (!dfs(i)){
for (int j = 0; j < sn; j++)
mark[S[j]] = false;
sn = 0;
if (!dfs(i + 1)) return false;
}
}
}
return true;
}
} gao;

const int N = 505;

int n, m, l[N], r[N];

int main() {
while (~scanf("%d%d", &n, &m)) {
gao.init(m);
for (int i = 0; i < m; i++) {
scanf("%d%d", &l[i], &r[i]);
if (l[i] > r[i]) swap(l[i], r[i]);
for (int j = 0; j < i; j++) {
if ((l[i] > l[j] && l[i] < r[j] && r[j] > l[i] && r[j] < r[i]) || (r[i] > l[j] && r[i] < r[j] && l[j] > l[i] && r[j] < r[i])) {