Graph Traversal Algorithm for Shortest Path Calculation

#include <bits/stdc++.h> #define maxn 1000 #define inf 1e9 #define mkp make_pair #define pii pair<int,int> #pragma GCC optimize(3,"Ofast","inline") using namespace std;

struct node { int a, b, t; } edge[maxn];

struct p { int num, t; } dis[maxn]; int head[maxn], nxt[maxn], b[maxn], tot;

void add(int a, int b, int c) {

edge[++tot] = {a, b, c};
nxt[tot] = head[a];
head[a] = tot;

}

int main() { ios::sync_with_stdio(false); cin.tie(0), cout.tie(0); int n, m; cin>>m>>n; string s; getline(cin,s); int x; for (int j = 1; j <= m; j++) { s=""; getline(cin, s); vector<int> v(0); x = 0; for (int i = 0; i < s.size(); i++) { if (s[i] != ' ') { x *= 10; x += s[i] - '0'; } else { v.push_back(x); x = 0; } } if (x) v.push_back(x); for (int i = 1; i < v.size(); i++) add(v[i - 1], v[i], j); } memset(dis, 0x3f, sizeof(dis)); queue<int> q; q.push(1); dis[1] = {0, 0}; while (!q.empty()) { int num = q.front(); q.po

It looks like you have a partial implementation of a graph traversal algorithm, possibly for finding the shortest path in a graph with some constraints. Let's complete the code and ensure it works correctly.

Here's the complete code:

#include <bits/stdc++.h>
#define maxn 1000
#define inf 1e9
#define mkp make_pair
#define pii pair<int,int>
#pragma GCC optimize(3,"Ofast","inline")
using namespace std;

struct node {
    int a, b, t;
} edge[maxn];

struct p {
    int num, t;
} dis[maxn];

int head[maxn], nxt[maxn], tot;

void add(int a, int b, int c) {
    edge[++tot] = {a, b, c};
    nxt[tot] = head[a];
    head[a] = tot;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int n, m;
    cin >> m >> n;
    string s;
    getline(cin, s); // To consume the newline character after reading n

    int x;
    for (int j = 1; j <= m; j++) {
        s = "";
        getline(cin, s);
        vector<int> v;
        x = 0;
        for (int i = 0; i < s.size(); i++) {
            if (s[i] != ' ') {
                x *= 10;
                x += s[i] - '0';
            } else {
                v.push_back(x);
                x = 0;
            }
        }
        if (x) v.push_back(x);
        for (int i = 1; i < v.size(); i++) {
            add(v[i - 1], v[i], j);
        }
    }

    memset(dis, 0x3f, sizeof(dis));
    queue<int> q;
    q.push(1);
    dis[1] = {0, 0};

    while (!q.empty()) {
        int num = q.front();
        q.pop();
        for (int i = head[num]; i; i = nxt[i]) {
            int to = edge[i].b;
            int t = edge[i].t;
            if (dis[to].num > dis[num].num + 1 || (dis[to].num == dis[num].num + 1 && dis[to].t > dis[num].t + t)) {
                dis[to] = {dis[num].num + 1, dis[num].t + t};
                q.push(to);
            }
        }
    }

    if (dis[n].num == 0x3f3f3f3f) {
        cout << -1 << endl;
    } else {
        cout << dis[n].num << " " << dis[n].t << endl;
    }

    return 0;
}

Explanation:

1. Input Reading:

   • The program reads the number of edges m and the number of nodes n.
   • It then reads m lines, each containing a sequence of integers representing the nodes connected by the edges.

2. Graph Construction:

   • The add function is used to add edges to the graph. Each edge is stored in the edge array, and the adjacency list is maintained using the head and nxt arrays.

3. Shortest Path Calculation:

   • The program uses a modified BFS to find the shortest path from node 1 to node n.
   • The dis array keeps track of the minimum number of edges (num) and the total weight (t) to reach each node.
   • The BFS updates the dis array and pushes nodes into the queue if a shorter path is found.

4. Output:

   • If the destination node n is unreachable, it prints -1.
   • Otherwise, it prints the minimum number of edges and the total weight of the shortest path.

This code should work correctly for the given problem constraints. Make sure to test it with various inputs to ensure its correctness.