UVa1607 poj1435 UVaLive1686 Gates

填坑系列(p.246)

由函数连续性得满足二分性

 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<algorithm>
 #include<iostream>

 using namespace std;

 void setIO(const string& s) {
     freopen((s + ".in").c_str(), "r", stdin);
     freopen((s + ".out").c_str(), "w", stdout);
 }
 template<typename Q> Q read(Q& x) {
     static char c, f;
     for(f = ; c = getchar(), !isdigit(c); ) if(c == '-') f = ;
     for(x = ; isdigit(c); c = getchar()) x = x *  + c - '';
     if(f) x = -x;
     return x;
 }
 template<typename Q> Q read() {
     static Q x; read(x); return x;
 }

 const int N =  + ;

 int n, m;
 struct Gates {
     int a, b, o;
 }gates[N];

 int output(int k) {
     for(int i = ; i <= m; i++) {
         int a = gates[i].a;
         int b = gates[i].b;
         int va = a <  ? -a > k : gates[a].o;
         int vb = b <  ? -b > k : gates[b].o;
         gates[i].o = !(va && vb);
     }
     return gates[m].o;
 }

 int solve(int vn) {
     int L = , R = n;
     while(L < R) {
         int mid = L + (R - L) / ;
         if(output(mid) == vn) R = mid; else L = mid + ;
     }
     return L;
 }

 int main() {
 #ifdef DEBUG
     freopen("in.txt", "r", stdin);
     freopen("out.txt", "w", stdout);
 #endif

     int T; scanf("%d", &T);
     while(T--) {
         scanf("%d%d", &n, &m);
         for(int i = ; i <= m; i++) {
             scanf("%d%d", &gates[i].a, &gates[i].b);
         }
         int v0 = output(), vn = output(n);
         if(v0 == vn) for(int i = ; i <= n; i++) putchar('');
         else {
             int p = solve(vn);
             for(int i = ; i < p; i++) putchar('');
             putchar('x');
             for(int i = p + ; i <= n; i++) putchar('');
         }
         puts("");
     }

     return ;
 }