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luoguTST：129ms

CODE：

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<queue>
 5 #define inf 2147483647
 6 #define ms(a,b) memset(a,b,sizeof a)
 7 #define rep(i,a,n) for(int i = a;i <= n;i++)
 8 #define per(i,n,a) for(int i = n;i >= a;i--)
 9 using namespace std;
10 typedef long long ll;
11 int read() {
12     int as = 0,fu = 1;
13     char c = getchar();
14     while(c < '0' || c > '9') {
15         if(c == '-') fu = -1;
16         c = getchar();
17     }
18     while(c >= '0' && c <= '9') {
19         as = as * 10 + c - '0';
20         c = getchar();
21     }
22     return as * fu;
23 }
24 const int N = 200005;
25 //head
26 int n,m,s,t;
27 int head[N],cst[N],nxt[N],mo[N],cnt = -1,ans;
28 int cur[N];
29 inline void add(int x,int y,int w) {
30     mo[++cnt] = y;
31     cst[cnt] = w;
32     nxt[cnt] = head[x];
33     head[x] = cnt;
34     return;
35 }
36 
37 int dep[N];
38 inline int dfs(int x,int lim) {
39     if(x == t || !lim) return lim;
40     int ret = 0;
41     for(int& i = cur[x]; i != -1; i = nxt[i]) {
42         int sn = mo[i];
43         if(dep[sn] == dep[x] + 1 && cst[i]) {
44             int dis = dfs(sn,min(lim,cst[i]));
45             if(dis) {
46                 cst[i] -= dis;
47                 cst[i^1] += dis;
48                 ret += dis,lim -= dis;
49                 if(!lim) break;
50             }
51         }
52     }
53     return ret;
54 }
55 
56 queue <int> q;
57 inline bool bfs() {
58     while(!q.empty()) q.pop();
59     ms(dep,0);
60     dep[s] = 1;
61     q.push(s);
62     while(!q.empty()) {
63         int x = q.front();
64         q.pop();
65         for(int i = head[x]; i != -1; i = nxt[i]) {
66             if(cst[i] && !dep[mo[i]]) {
67                 dep[mo[i]] = dep[x] + 1;
68                 q.push(mo[i]);
69             }
70         }
71     }
72     return dep[t];
73 }
74 
75 inline void init() {
76     n = read();
77     m = read();
78     s = read();
79     t = read();
80     ms(head,-1);
81     ms(nxt,-1);
82     rep(i,1,m) {
83         int x = read();
84         int y = read();
85         int w = read();
86         add(x,y,w),add(y,x,0);
87     }
88 }
89 
90 int main() {
91     init();
92     while(bfs()) {
93         rep(i,1,n) cur[i] = head[i];
94         ans += dfs(s,inf);
95     }
96     printf("%d\n",ans);
97     return 0;
98 }

 

posted @ 2018-10-03 22:22  白怀潇  阅读(116)  评论(0)    收藏  举报