From b97593b9d99d5282d7f39a787798776dfc63ffa8 Mon Sep 17 00:00:00 2001
From: vijay532 <sahaniv66@gmail.com>
Date: Tue, 1 Oct 2019 22:11:12 +0530
Subject: [PATCH] https://www.spoj.com/problems/ELEVTRBL/

---
 ELEVTRBL.cpp | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 ELEVTRBL.cpp

diff --git a/ELEVTRBL.cpp b/ELEVTRBL.cpp
new file mode 100644
index 0000000..8104a30
--- /dev/null
+++ b/ELEVTRBL.cpp
@@ -0,0 +1,56 @@
+//g++  5.4.0
+ 
+#include <bits/stdc++.h>
+#define ll long long 
+using namespace std;
+/*
+10 1 10 2 1
+*/
+ll s,g,u,d,f;
+ll mark[1000001];
+ll dist[1000001];
+void compute()
+{
+    //cout<<s<<" "<<f<<" "<<g<<u<<d;
+    ll current,next_up,next_down;
+    queue<ll>q;
+    q.push(s);
+    dist[s]=0;
+    mark[s]=1;
+    while(!q.empty())
+    {
+        current=q.front();
+        q.pop();
+        next_up=current+u;
+        next_down=current-d;
+        //cout<<next_up<<" "<<next_down<<" ";
+        while(next_up<=f && !mark[next_up])
+        {
+            mark[next_up]=1;
+            q.push(next_up);
+            dist[next_up]=dist[current]+1;
+        }
+        while(next_down>=1 && !mark[next_down])
+        {
+            mark[next_down]=1;
+            q.push(next_down);
+            dist[next_down]=dist[current]+1;
+        }
+        //cout<<q.size()<<endl;
+    }
+    return ;
+}
+int main()
+{
+    cin>>f>>s>>g>>u>>d;   
+    dist[g]=-1;
+    compute();
+    if(dist[g]==-1)
+    {
+        cout<<"use the stairs";
+    }
+    else
+    {
+        cout<<dist[g];
+    }
+} 
\ No newline at end of file