题意非常难理解……
#include<cstdio>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;const int MAXN = 212345;
struct node
{int a, b, w;
}g[MAXN];
int n, m;int output(int k)
{REP(i, 1, m + 1){int a = g[i].a;int b = g[i].b;int va = a < 0 ? -a > k : g[a].w;int vb = b < 0 ? -b > k : g[b].w;g[i].w = !(va && vb);}return g[m].w;
}int solve(int vn)
{int l = 0, r = n + 1;while(l + 1 < r){int mid = (l + r) >> 1;if(output(mid) == vn) r = mid;else l = mid;}return r;
}int main()
{int T;scanf("%d", &T);while(T--){scanf("%d%d", &n, &m);REP(i, 1, m + 1) scanf("%d%d", &g[i].a, &g[i].b);int v0 = output(0);int vn = output(n);if(v0 == vn){REP(i, 1, n + 1) putchar('0');puts(""); continue;}int x = solve(vn);REP(i, 1, x) putchar('0');putchar('x');REP(i, x + 1, n + 1) putchar('1');puts("");}return 0;
}