Cod sursa(job #2427928)

Utilizator Alex18maiAlex Enache Alex18mai Data 2 iunie 2019 21:28:40
Problema Flux maxim Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.75 kb
//ALEX ENACHE

#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
#include <unordered_map>
#include <time.h>
#include <iomanip>
#include <deque>
#include <math.h>
#include <assert.h>
#include <stack>
#include <bitset>
#include <random>
#include <chrono>

using namespace std;

const double PI = acos(-1);
const double eps = 1e-6;

inline long long lgput(long long a , long long b , long long mod) {
    long long ret = 1;
    while( b ){
        if(b & 1) ret = (ret * a) % mod;
        a = (a * a) % mod;
        b >>= 1;
    }

    return (ret%mod);
}

inline long long inv(long long x , long long MOD) {
    return lgput(x, MOD - 2, MOD);
}

inline bool exist (double nr){
    return (nr < -eps) || (nr > eps);
}

long long big_rand(){
    return rand () * RAND_MAX + rand();
}

//-----------------------------------------------------------------

//#include <iostream>
#include <fstream>
ifstream cin ("maxflow.in");ofstream cout ("maxflow.out");

int n;
vector < int > gr[1010];
int cap[1010][1010];
int flow[1010][1010];
int dad[1010];

queue < int > q;

bool bfs(){

    for (int i=1; i<=n; i++){
        dad[i] = 0;
    }

    bool ok = 0;
    q.push(1);
    dad[1] = -1;
    while (!q.empty()){
        int now = q.front();
        q.pop();
        if (now == n){
            ok = 1;
            continue;
        }
        for (auto &x : gr[now]){
            if (flow[now][x] < cap[now][x] && !dad[x]){
                dad[x] = now;
                q.push(x);
            }
        }
    }
    return ok;
}

int main() {

    //freopen("input", "r", stdin);freopen("output", "w", stdout);

    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cout << setprecision(10) << fixed;
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    srand(time(nullptr));

    int m;
    cin>>n>>m;

    for (int i=1; i<=m; i++){
        int a , b , c;
        cin>>a>>b>>c;
        gr[a].push_back(b);
        gr[b].push_back(a);
        cap[a][b] += c;
    }

    int ans = 0;
    while (bfs()){
        for (auto &x : gr[n]){
            if (dad[x]){
                dad[n] = x;
                int MIN = 1e9;
                int now = n;
                while (now != 1){
                    MIN = min(MIN , cap[dad[now]][now] - flow[dad[now]][now]);
                    now = dad[now];
                }
                ans+=MIN;
                now = n;
                while (now != 1){
                    flow[dad[now]][now] += MIN;
                    flow[now][dad[now]] -= MIN;
                    now = dad[now];
                }
            }
        }
    }

    cout<<ans;

    return 0;
}