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Author: ayush933

c_plus_plus/4yush933/4yush933_MessageRoute.cpp

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+// author: 4yush933
+// problem: https://cses.fi/problemset/task/1667/
+// Sol: https://cses.fi/problemset/result/1028819/
+// Question: Finding shortest path between two nodes in a graph
+#pragma GCC optimize("O3")  
+#include <bits/stdc++.h>
+#include <fstream>
+using namespace std;
+typedef long long ll;
+#define F first
+#define pii pair<int,int>
+#define S second
+#define endl "\n"
+#define gcd(a,b) __gcd(a,b)
+#define lcm(a,b) (a*b)/gcd(a,b)
+#define mem(z,i) memset(z,i,sizeof(z))
+#define eps 1e-7
+#define I (int)
+#define mod 1000000007 
+#define pb push_back
+const long long INF = 1000000000000000000LL;
+template <typename Type>
+ostream &operator<<(ostream &out, vector<Type> &vec) {
+    for (auto val : vec)
+        out << val << " ";
+    return out;
+}
+//const int WASTE=∞;
+ll power(ll a,ll b){
+	ll i=1;
+	while(b){
+		if(b%2)
+			i=(i*a)%mod;
+		b/=2;
+		a=(a*a)%mod;
+	}
+	return i;
+}
+ll mulmod(ll a, ll b) { 
+    ll res = 0;
+    a = a % mod; 
+    while (b > 0) {
+        if (b % 2 == 1) 
+            res = (res + a) % mod; 
+        a = (a * 2) % mod; 
+        b /= 2; 
+    }
+    return res % mod; 
+} 	
+const int N=1e5+5;
+signed main() {
+    ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
+  	// cout<<fixed;
+  	// cout.precision(10);
+  	// ifstream cin  ("alchemy_input.txt");
+  	// ofstream cout ("out.txt");
+  	//#define int ll
+   	int n,m;
+   	cin>>n>>m;
+   	vector<int>adj[N];
+   	while(m--){
+   		int a,b;
+   		cin>>a>>b;
+   		adj[a].pb(b); adj[b].pb(a);
+   	}
+   	int d[n+1],p[n+1];
+   	for(int x=2;x<=n;x++)
+   		d[x]=mod;
+   	queue<int>q;
+   	q.push(1); d[1]=1;
+   	while(!q.empty()){
+   		int x=q.front(); q.pop();
+   		for(int y:adj[x]){
+   			if(d[y]==mod) q.push(y);
+   			if(d[x]+1<d[y]) d[y]=d[x]+1,p[y]=x;
+   		}
+   	}
+   	if(d[n]==mod) cout<<"IMPOSSIBLE";
+   	else{
+   		cout<<d[n]<<endl;
+   		int i=n; vector<int>v;
+   		while(i!=1){
+   			v.pb(i); i=p[i];
+   		}
+   		v.pb(1);
+   		reverse(begin(v),end(v));
+   		cout<<v;
+   	}
+  	return 0;
+}
+// Profile:https://cses.fi/user/13405