C++ Code：（ISAP）
#include <cstdio>
#include <cstring>
#define maxn 1210
#define maxm 120010
int n, m, st, ed;
const int inf = 0x7fffffff;
inline int min(int a, int b) {return a < b ? a : b;}
namespace Network_Flow {
int st, ed, MF, n;
int head[maxn], cnt = 2;
struct Edge {
int to, nxt, w;
} e[maxm << 1];
inline void addE(int a, int b, int c) {
e[cnt] = (Edge) {b, head[a], c}; head[a] = cnt;
e[cnt ^ 1] = (Edge) {a, head[b], 0}; head[b] = cnt ^ 1;
cnt += 2;
}
int GAP[maxn], d[maxn];
int last[maxn];
int q[maxn], h, t;
inline void init() {
GAP[d[ed] = 1] = 1;
for (int i = 1; i <= n; i++) last[i] = head[i];
q[h = t = 0] = ed;
while (h <= t) {
int u = q[h++];
for (int i = head[u]; i; i = e[i].nxt) {
int v = e[i].to;
if (!d[v]) {
d[v] = d[u] + 1;
GAP[d[v]]++;
q[++t] = v;
}
}
}
}
int dfs(int u, int low) {
if (!low || u == ed) return low;
int w, res = 0;
for (int &i = last[u]; i; i = e[i].nxt) {
int v = e[i].to;
if (d[u] == d[v] + 1) {
w = dfs(v, min(low, e[i].w));
res += w, low -= w;
e[i].w -= w, e[i ^ 1].w += w;
if (!low) return res;
}
}
if (!(--GAP[d[u]])) d[st] = n + 1;
++GAP[++d[u]], last[u] = head[u];
return res;
}
inline void ISAP(int S, int T) {
st = S, ed = T;
init();
while (d[st] <= n) MF += dfs(st, inf);
}
inline void clear() {
memset(head, 0, sizeof head); cnt = 2;
memset(GAP, 0, sizeof GAP);
memset(d, 0, sizeof d);
MF = 0;
}
}
#define read() R::READ()
#include <cctype>
namespace R {
int x;
#ifdef ONLINE_JUGER
#define M 1 << 25
char op[M], *ch;
inline void init() {
fread(ch = op, 1, M, stdin);
}
inline int READ() {
while (isspace(*ch)) ch++;
for (x = *ch & 15, ch++; isdigit(*ch); ch++) x = x * 10 + (*ch & 15);
return x;
}
#undef M
#else
char ch;
inline int READ() {
ch = getchar();
while (isspace(ch)) ch = getchar();
for (x = ch & 15, ch = getchar(); isdigit(ch); ch = getchar()) x = x * 10 + (ch & 15);
return x;
}
#endif
}
int main() {
#ifdef ONLINE_JUGER
R::init();
#endif
n = read(), m = read(), st = read(), ed = read();
Network_Flow::n = n;
for (int i = 0, a, b, c; i < m; i++) {
a = read(), b = read(), c = read();
Network_Flow::addE(a, b, c);
}
Network_Flow::ISAP(st, ed);
printf("%d\n", Network_Flow::MF);
return 0;
}