Cod sursa(job #3296335)

Utilizator RaresHRares Hanganu RaresH Data 12 mai 2025 12:04:48
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 3.97 kb
#pragma GCC optimize("O3", "unroll-loops")
#pragma GCC target("avx2")
#include <fstream>
#include <queue>

const int MAX_N = 50'000;
const int INF = 2'000'000'000;
const int MAX_M = 250'000;
const int NIL = -1;

class InParser {
private:
	FILE * fin;
	char * buff;
	int sp;

	char read_ch() {
		++sp;
		if(sp == 16384) {
			sp = 0;
			fread(buff, 1, 16384, fin);
		}
		return buff[sp];
	}

public:
	InParser(const char * nume) {
		fin = fopen(nume, "r");
		buff = new char[16384]();
		sp = 4095;
	}

	InParser& operator >> (int &n) {
		char c;
		while(!isdigit(c = read_ch()) && c != '-');
		int sgn = 1;
		if(c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while(isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}

	InParser& operator >> (long long &n) {
		char c;
		n = 0;
		while(!isdigit(c = read_ch()) && c != '-');
		long long sgn = 1;
		if(c == '-') {
			n = 0;
			sgn = -1;
		} else {
			n = c - '0';
		}
		while(isdigit(c = read_ch())) {
			n = 10 * n + c - '0';
		}
		n *= sgn;
		return *this;
	}
};
InParser fin("dijkstra.in");
std::ofstream fout("dijkstra.out");

struct Edge {
  int node;
  int cost;
};

struct State {
  int node;
  int cost;

  bool operator<(const State &other) const {
    return cost > other.cost;
  }
};

struct Heap {
  int n;
  State v[MAX_N + 1];
  int where[MAX_N];

  void init(int _n) {
    n = 0;
    for(int i = 0; i < _n; i++) {
      where[i] = -1;
    }
  }

  void sift_down(int node) {
    while(2 * node <= n) {
      State left = v[2 * node];
      int next;
      if(2 * node + 1 > n) {
        if(left < v[node]) {
          break;
        }
        next = 2 * node;
      } else {
        State right = v[2 * node + 1];
        if(left < right) {
          if(right < v[node]) {
            break;
          }
          next = 2 * node + 1;
        } else {
          if(left < v[node]) {
            break;
          }
          next = 2 * node;
        }
      }
      std::swap(where[v[node].node], where[v[next].node]);
      std::swap(v[node], v[next]);
      node = next;
    }
  }

  void sift_up(int node) {
    while(node > 1 && v[node / 2] < v[node]) {
      std::swap(where[v[node].node], where[v[node / 2].node]);
      std::swap(v[node], v[node / 2]);
      node /= 2;
    }
  }

  void push(State val) {
    int pos = where[val.node];
    if(pos == -1) {
      where[val.node] = ++n;
      v[n] = val;
      sift_up(n);
    } else {
      v[pos].cost = val.cost;
      sift_up(pos);
    }
  }

  State top() {
    return v[1];
  }

  void pop() {
    std::swap(where[v[1].node], where[v[n].node]);
    std::swap(v[1], v[n]);
    n--;
    sift_down(1);
  }

  bool empty() {
    return n == 0;
  }
};

struct ListNode {
  Edge e;
  int next;
};

int n;
std::vector<Edge> adj[MAX_N];
int min_cost[MAX_N];
Heap pq;
int head[MAX_N];
int ptr;
ListNode nodes[MAX_M];

void dijkstra(int source) {
  for(int i = 0; i < n; i++) {
    min_cost[i] = INF;
  }

  pq.init(n);
  min_cost[source] = 0;
  pq.push({source, 0});
  while(!pq.empty()) {
    State nd = pq.top();
    pq.pop();
    int pos = head[nd.node];
    while(pos != NIL) {
      Edge e = nodes[pos].e;
      int c = nd.cost + e.cost;
      if(c < min_cost[e.node]) {
        min_cost[e.node] = c;
        pq.push({e.node, c});
      }
      pos = nodes[pos].next;
    }
  }
}

void add_edge(int u, int v, int cost) {
  nodes[ptr] = {{v, cost}, head[u]};
  head[u] = ptr;
  ptr++;
}

int main() {
  int m;
  fin >> n >> m;

  for(int i = 0; i < n; i++) {
    head[i] = NIL;
  }

  ptr = 0;
  for(int i = 0; i < m; i++) {
    int u, v, cost;
    fin >> u >> v >> cost;
    u--;
    v--;
    add_edge(u, v, cost);
  }

  dijkstra(0);

  for(int i = 1; i < n; i++) {
    fout << (min_cost[i] == INF ? 0 : min_cost[i]) << " ";
  }
  fout << "\n";

  return 0;
}