1 #include <cstdio>
2 #include <cstring>
3 #include <algorithm>
4 #include <queue>
5 using namespace std;
6 const int INF = 0x3f3f3f3f;
7 const int N = 10005;
8 const int M = 100005;
9 struct type{
10 int u, v, w, next;
11 }edge[M << 1];
12 int head[N], cnt;
13 int dep[N], cur[N];
14 int n, m, s, t, d;
15 void add(int x, int y, int z){
16 edge[cnt].u = x;
17 edge[cnt].v = y;
18 edge[cnt].w = z;
19 edge[cnt].next = head[x];
20 head[x] = cnt;
21 cnt++;
22 }
23 bool bfs(){
24 int fro = 0;
25 queue<int> q;
26 q.push(s);
27 for(int i = 1; i <= n; i++) dep[i] = 0;
28 dep[s] = 1;//important!!!!!
29 while(!q.empty()){
30 fro = q.front(); q.pop();
31 for(int i = head[fro]; i != -1; i = edge[i].next){
32 int vv = edge[i].v;
33 if(!dep[vv] && edge[i].w > 0){
34 dep[vv] = dep[fro] + 1;
35 q.push(vv);
36 }
37 }
38 }
39 return dep[t] ? 1 : 0;
40 }
41 int dfs(int x, int rest){
42 if(x == t || !rest) return rest;
43 for(int& i = cur[x]; i != -1; i = edge[i].next){//当前弧优化
44 int vv = edge[i].v, ww = edge[i].w;
45 if(dep[vv] != dep[x] + 1) continue;
46 d = dfs(vv, min(rest, ww));
47 if(d > 0){
48 edge[i].w -= d;
49 edge[i ^ 1].w += d;
50 return d;
51 }
52 }
53 return 0;
54 }
55 int dinic(){
56 int ans = 0;
57 while(bfs()){
58 for(int i = 1; i <= n; i++) cur[i] = head[i];//当前弧优化
59 if(d = dfs(s, INF)){
60 ans += d;
61 }
62 }
63 return ans;
64 }
65 int main() {
66 int x, y, z;
67 scanf("%d%d%d%d", &n, &m, &s, &t);
68 for(int i = 1; i <= n; i++) head[i] = -1;
69 for(int i = 1; i <= m; i++){
70 scanf("%d%d%d", &x, &y, &z);
71 add(x, y, z);
72 add(y, x, 0);
73 }
74 printf("%d", dinic());
75 return 0;
76 }
最大流dinic
1 #include <cstdio>
2 #include <cstring>
3 #include <algorithm>
4 #include <queue>
5 using namespace std;
6 const int INF = 0x3f3f3f3f;
7 const int N = 5005;
8 const int M = 50005;
9 struct type{
10 int u, v, w, f, next;
11 }edge[M << 1];
12 struct type2{
13 int f, cur, incf;
14 bool vis;
15 }ser[N];
16 int head[N], cnt;
17 int n, m, s, t;
18 int max_flow, min_cost;
19 void add(int x, int y, int z, int zz){
20 edge[cnt].u = x;
21 edge[cnt].v = y;
22 edge[cnt].w = z;
23 edge[cnt].f = zz;
24 edge[cnt].next = head[x];
25 head[x] = cnt;
26 cnt++;
27 }
28 bool spfa(){
29 for(int i = 1; i <= n; i++){
30 ser[i].vis = 0;
31 ser[i].f = INF;
32 }
33 ser[s].f = 0;
34 ser[s].incf = INF;
35 int fro;
36 queue<int> q;
37 q.push(s);
38 while(!q.empty()){
39 fro = q.front(); q.pop(); ser[fro].vis = 0;
40 for(int i = head[fro]; i != -1; i = edge[i].next){
41 int vv = edge[i].v, ww = edge[i].w, ff = edge[i].f;
42 if(ww > 0 && ser[fro].f + ff < ser[vv].f){
43 ser[vv].f = ser[fro].f + ff;
44 ser[vv].incf = min(ser[fro].incf, ww);
45 ser[vv].cur = i;
46 if(!ser[vv].vis){
47 ser[vv].vis = 1;
48 q.push(vv);
49 }
50 }
51 }
52 }
53 return ser[t].f == INF ? 0 : 1;
54 }
55 void update(){
56 int i = t, j;
57 while(i != s){
58 j = ser[i].cur;
59 edge[j].w -= ser[t].incf;
60 edge[j ^ 1].w += ser[t].incf;
61 i = edge[j].u;
62 }
63 max_flow += ser[t].incf;
64 min_cost += ser[t].f * ser[t].incf;
65 }
66 void EK(){
67 while(spfa()){
68 update();
69 }
70 }
71 int main() {
72 //freopen("testdata.in", "r", stdin);
73 //freopen("testdata.out", "w", stdout);
74 int x, y, z, zz;
75 scanf("%d%d%d%d", &n, &m, &s, &t);
76 for(int i = 1; i <= n; i++) head[i] = -1;
77 for(int i = 1; i <= m; i++){
78 scanf("%d%d%d%d", &x, &y, &z, &zz);
79 add(x, y, z, zz);
80 add(y, x, 0, -zz);
81 }
82 EK();
83 printf("%d %d\n", max_flow, min_cost);
84 return 0;
85 }
最小费用最大流EK
原文地址：https://www.cnblogs.com/hjmmm/p/9261480.html
时间： 2024-11-26 07:50:47