有没有ISAP算法代码
时间: 2023-07-03 14:13:52 浏览: 62
当然有,以下是一个简单的ISAP算法的实现代码,可以用于求解最大流问题:
```
#include <bits/stdc++.h>
using namespace std;
const int INF = 0x7fffffff;
const int MAXN = 1005;
const int MAXM = 100005;
struct Edge {
int to, next, cap;
} edge[MAXM << 1];
int head[MAXN], cur[MAXN], dep[MAXN];
int n, m, s, t, tot = 1;
void addEdge(int u, int v, int c) {
edge[++tot] = {v, head[u], c};
head[u] = tot;
edge[++tot] = {u, head[v], 0};
head[v] = tot;
}
bool bfs() {
memset(dep, -1, sizeof(dep));
queue<int> q;
q.push(t);
dep[t] = 0;
while (!q.empty()) {
int u = q.front();
q.pop();
for (int i = head[u]; i; i = edge[i].next) {
int v = edge[i].to;
if (dep[v] == -1 && edge[i ^ 1].cap) {
dep[v] = dep[u] + 1;
q.push(v);
}
}
}
return dep[s] != -1;
}
int dfs(int u, int flow) {
if (u == t) return flow;
for (int &i = cur[u]; i; i = edge[i].next) {
int v = edge[i].to;
if (dep[v] == dep[u] - 1 && edge[i].cap) {
int f = dfs(v, min(flow, edge[i].cap));
if (f) {
edge[i].cap -= f;
edge[i ^ 1].cap += f;
return f;
}
}
}
return 0;
}
int isap() {
int maxflow = 0, flow;
while (bfs()) {
memcpy(cur, head, sizeof(head));
while (flow = dfs(s, INF)) {
maxflow += flow;
}
}
return maxflow;
}
int main() {
scanf("%d%d%d%d", &n, &m, &s, &t);
for (int i = 1; i <= m; i++) {
int u, v, c;
scanf("%d%d%d", &u, &v, &c);
addEdge(u, v, c);
}
printf("%d\n", isap());
return 0;
}
```
这是一个基于邻接表的实现,其中`s`为源点编号,`t`为汇点编号,`n`为节点数,`m`为边数。函数`addEdge`用于添加一条有向边,函数`bfs`用于建立分层图,函数`dfs`用于在分层图上寻找增广路径,函数`isap`则是整个算法的主体。
希望这个代码对你有所帮助!