Engulf @ 2022-08-01 21:42:12
rt,如果是数据改过说下
看到 EK 跑的都比我这个快,很是不解。
明早来看。
836ms
#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 205, M = 5005;
int n, m, s, t, maxflow;
int dep[N], flow[M << 1];
struct edge
{
int to, nxt;
}e[M << 1];
int head[N], idx = 1;
void add(int x, int y, int w) {e[ ++ idx] = {y, head[x]}, head[x] = idx, flow[idx] = w;}
bool bfs()
{
queue<int> q;
memset(dep, 0, sizeof dep);
q.push(s), dep[s] = 1;
while (!q.empty())
{
int u = q.front(); q.pop();
for (int i = head[u]; i; i = e[i].nxt)
{
int v = e[i].to;
if (flow[i] && !dep[v])
{
dep[v] = dep[u] + 1;
q.push(v);
}
}
}
return dep[t];
}
int dfs(int u, int in)
{
if (u == t) return in;
int out = 0;
for (int i = head[u]; i; i = e[i].nxt)
{
int v = e[i].to;
if (flow[i] && dep[v] == dep[u] + 1)
{
int fl = dfs(v, min(flow[i], in));
flow[i] -= fl, flow[i ^ 1] += fl;
in -= fl, out += fl;
}
}
if (!out) dep[u] = 0;
return out;
}
signed main()
{
scanf("%lld%lld%lld%lld", &n, &m, &s, &t);
for (int i = 1, x, y, w; i <= m; i ++ )
scanf("%lld%lld%lld", &x, &y, &w), add(x, y, w), add(y, x, 0);
while (bfs()) maxflow += dfs(s, 1e18);
printf("%lld\n", maxflow);
return 0;
}
by 8atemak1r @ 2022-08-01 21:49:18
@TMJYH09 你 dfs 的 for 循环条件里要加上 in
不为 0
by EastSnowLotus @ 2022-08-01 21:49:34
dinic 要算若干 bfs 和 dfs,应该会比较慢吧?
要是比其他 ACer 的也慢那才是代码有问题
by 8atemak1r @ 2022-08-01 21:49:39
不然你减来减去的没有意义啊
by 8atemak1r @ 2022-08-01 21:50:08
@CoCo_Candy 比我慢了快十倍(没记错的话
by EastSnowLotus @ 2022-08-01 21:50:11
@8atemak1r -0 珂海星
by 8atemak1r @ 2022-08-01 21:50:39
@CoCo_Candy 啥 -0
by 方123456 @ 2022-08-01 21:53:17
加了点小剪枝,类似搜不出来就不搜
by EastSnowLotus @ 2022-08-01 21:53:51
@8atemak1r
不然你减来减去的没有意义啊
减一堆 0 属于是(
by 方123456 @ 2022-08-01 21:54:41
加当前弧优化更快。
by jijidawang @ 2022-08-01 21:58:54
你们都在说啥,核心问题不是在于没加当前弧优化吗