【hihoCoder 第133周】【hihoCoder 1467】2-SAT·hihoCoder音乐节

http://hihocoder.com/problemset/problem/1467
2-sat模板。。。详细的题解请看题目里的提示。
tarjan模板打错again致命伤qwq

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int N = 103;
const int M = 1003;

bool inst[N << 1];
struct node {int nxt, to;} E[M << 1];
int cnt, point[N << 1], dfn[N << 1], low[N << 1], st[N << 1], top = 0, bel[N << 1];
void ins(int u, int v) {E[++cnt] = (node) {point[u], v}; point[u] = cnt;}

char A[23], B[23];
int n, m, a, b, ct, tot;

void tarjan(int x) {
	dfn[x] = low[x] = ++ct;
	inst[st[++top] = x] = true;
	for (int i = point[x], v = E[i].to; i; v = E[i = E[i].nxt].to)
		if (!dfn[v]) tarjan(v), low[x] = min(low[x], low[v]);
		else if (inst[v]) low[x] = min(low[x], dfn[v]);
	if (dfn[x] == low[x]) {
		++tot;
		while (st[top] != x) {
			inst[st[top]] = false;
			bel[st[top--]] = tot;
		}
		inst[x] = false;
		bel[st[top--]] = tot;
	}
}

int main() {
	int T; scanf("%d", &T);
	while (T--) {
		scanf("%d%d", &n, &m);
		int doublen = n << 1;
		memset(point, 0, sizeof(int) * doublen);
		memset(dfn, 0, sizeof(int) * doublen);
		ct = cnt = tot = 0;
		for (int i = 1; i <= m; ++i) {
			scanf("%s%s", A, B);
			int lena = strlen(A), lenb = strlen(B);
			a = b = 0;
			for (int j = 1; j < lena; ++j) a = a * 10 + A[j] - 48;
			for (int j = 1; j < lenb; ++j) b = b * 10 + B[j] - 48;
			--a; --b;
			if (A[0] == 'h') a += n;
			if (B[0] == 'h') b += n;
			ins((a + n) % doublen, b);
			ins((b + n) % doublen, a);
		}
		for (int i = 0; i < doublen; ++i)
			if (!dfn[i])
				tarjan(i);
		bool flag = false;
		for (int i = 0; i < n; ++i)
			if (bel[i] == bel[i + n]) {
				flag = true;
				puts("BAD");
				break;
			}
		if (!flag) puts("GOOD");
	}
	return 0;
}