hihoCoder#1139 二分·二分答案

原题地址

挺简单一道题，结果因为一时傻逼写错一个小地方，导致WA成狗了_(:з」∠)_

代码：

 #include <iostream>
 #include <cstring>
 #include <queue>

 using namespace std;

 #define MAX_V 10008
 #define MAX_E 200008

 int N, M, K, T;
 int f[MAX_V];
 bool v[MAX_V];
 int n[MAX_E];
 int w[MAX_E];
 int t[MAX_E];
 int max_w = ;;
 int min_w = ;

 bool check(int l) {
   queue<pair<int, int> > q;
   memset(v, , sizeof(v));
   q.push(pair<int, int>(, K));
   while (!q.empty()) {
     pair<int, int> p = q.front();
     q.pop();
     if (p.first == T && p.second >= )
       return true;
     if (p.second ==  || v[p.first])
       continue;
     v[p.first] = true;
     for (int i = f[p.first]; i != ; i = n[i]) {
       if (w[i] > l || v[t[i]])
         continue;
       q.push(pair<int, int>(t[i], p.second - ));
     }
   }
   return false;
 }

 int find(int l, int r) {
   int res = r;
   while (l <= r) {
     int m = (l + r) / ;
     if (check(m)) {
       res = m;
       r = m - ;
     }
     else
       l = m + ;
   }
   return res;
 }

 int main() {
   memset(n, , sizeof(n));
   scanf("%d%d%d%d", &N, &M, &K, &T);
   for (int i = , j = ; i < M; i++) {
     int a, b, c;
     scanf("%d%d%d", &a, &b, &c);
     min_w = min(min_w, c);
     max_w = max(max_w, c);
     j++;
     w[j] = c;
     t[j] = b;
     n[j] = f[a];
     f[a] = j;
     j++;
     w[j] = c;
     t[j] = a;
     n[j] = f[b];
     f[b] = j;
   }
   if (T == )
     printf("0\n");
   else
     printf("%d\n", find(min_w, max_w));
   return ;
 }