记录编号	603404	评测结果	AAAAAAAAAA
题目名称	3319. [USACO19 DEC Gold]Milk Pumping	最终得分	100
用户昵称	LikableP	是否通过	通过
代码语言	C++	运行时间	0.149 s
提交时间	2025-07-11 16:30:57	内存使用	3.70 MiB

#include <cstdio>
#include <cstring>
#include <queue>
#include <utility>

void ParseIn();
void Core();
void WriteOut();

int main() {
  freopen("pump.in", "r", stdin);
  freopen("pump.out", "w", stdout);
  ParseIn();
  Core();
  WriteOut();
  return 0;
}

template <typename T> T read();
template <typename T> void write(T, char);
template <typename T> T max(T, T);
void AddEdge(int, int, int, int);
int Dijkstra(int, int, int);

const int MAXN = 1010;

int n, m;

void ParseIn() {
  n = read<int>(), m = read<int>();
  for (int i = 1; i <= m; ++i) {
    int u = read<int>(), v = read<int>(), w = read<int>(), f = read<int>();
    AddEdge(u, v, w, f);
    AddEdge(v, u, w, f);
  }
}

double ans = 0;
void Core() {
  int l = 1, r = 1000;
  // while (l < r) {
  for (int mid = 1; mid <= 1000; ++mid) {
    // int mid = l + ((r - l) >> 1);
    int cost = Dijkstra(1, mid, n);
    if (cost == 0x3f3f3f3f) {
      r = mid - 1;
    } else {
      ans = max(ans, mid / 1.0 / cost);
      l = mid + 1;
    }
  }
}

void WriteOut() {
  write((long long) (ans * 1000000), '\n');
}

struct EDGE {
  int v, w, f, next;
} edge[MAXN << 1];
int head[MAXN], edgeNum;
int dis[MAXN];
bool vis[MAXN];
::std::priority_queue<::std::pair<int, int>> pq;
int Dijkstra(int st, int mid, int ed) {
  memset(dis, 0x3f, sizeof dis);
  memset(vis, 0, sizeof vis);
  dis[st] = 0;
  pq.push(::std::make_pair(0, st));
  while (!pq.empty()) {
    int u = pq.top().second;
    pq.pop();
    if (vis[u]) continue;
    vis[u] = true;
    for (int i = head[u]; i; i = edge[i].next) {
      int v = edge[i].v, w = edge[i].w, f = edge[i].f;
      if (f < mid) continue;
      if (dis[u] + w < dis[v]) {
        dis[v] = dis[u] + w;
        pq.push(::std::make_pair(-dis[v], v));
      }
    }
  }
  return dis[ed];
}

void AddEdge(int u, int v, int w, int f) {
  edge[++edgeNum] = {v, w, f, head[u]};
  head[u] = edgeNum;
}

template <typename T> T max(T x, T y) {
  return x > y ? x : y;
}

#define isdigit(ch) (ch >= '0' && ch <= '9')
template <typename T> T read() {
  T res = 0, f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar())
    if (ch == '-') f = -1;
  for (; isdigit(ch); ch = getchar()) res = (res << 3) + (res << 1) + (ch ^ 48);
  return res * f;
}
#undef isdigit

template <typename T> void write(T x, char ed) {
  if (x < 0) x = -x, putchar('-');
  int sta[sizeof(T) << 2], top = 0;
  do {
    sta[++top] = x % 10;
    x /= 10;
  } while (x);
  while (top) {
    putchar(sta[top--] ^ 48);
  }
  putchar(ed);
}