Added Flappy bird problem

Author: Karnika06

Codechef Problems/FlappyBird.java

@@ -0,0 +1,118 @@
+
+/*
+ *Implementation 'Flappy Bird' problem from June CodeChef starters
+ *
+ *Problem name : Flappy Bird
+ *Problem code : FLAPPYBD
+ *Problem link : https://www.codechef.com/START5C/problems/FLAPPYBD/
+ *
+ */
+
+import java.util.*;
+import java.lang.*;
+import java.io.*;
+
+//In this problem we need to tell Chef if he can win the game (get the bird 
+//to cross all the obstacles) and the minimum number of clicks required to win in such a case
+
+public class FlappyBird
+{
+    public static void main() 
+    {
+        Scanner sc = new Scanner(System.in);
+        int t = sc.nextInt();
+        while(t-->0)
+        {
+            //Number of obstacles
+            int n = sc.nextInt();             
+            
+            //The bird starts at a height H
+            int H = sc.nextInt();             
+            int position[] = new int[n];     
+            int heights[] = new int[n];      
+            
+            //Position of obstacles
+            for(int i=0;i < n;i++) 
+            position[i]=sc.nextInt();       
+
+            //Height of obstacles
+            for(int i=0 ; i < n ; i++)
+            heights[i] = sc.nextInt();        
+        
+            int i = 0;
+            int pos = 0;
+            int h = H;
+            int nc = 0;
+            boolean win = true;
+            int rem;
+            int ex;
+            int ans = 0;
+            
+            //For each integer i (0≤i<xN), Chef has the option to click once when 
+            //the bird is at x=i. Let's denote the bird's height (y-coordinate) at 
+            //that point by j. If he clicks, the bird moves to x=i+1 and y=j+1. 
+            //Otherwise, the bird moves to x=i+1 and y=j−1.
+            while(i < n) 
+            {
+                int dist = position[i] - pos;
+                h -= dist;
+                nc += dist;
+                if(h <= heights[i])     
+                {
+                    rem = heights[i]+1-h;
+                    if(2 * nc < rem)
+                    {
+                        //print −1  if it is impossible to cross all the obstacles
+                        System.out.println("-1");   
+                        win = false;
+                        break;
+                    }
+                    else 
+                    {
+                        ex = rem/2 + rem%2;
+                        nc -= ex;
+                        
+                        //the minimum number of clicks required to cross all the obstacles successfully
+                        ans += ex;      
+                        h = h + 2 * ex;
+                        pos = position[i];
+                        i++; 
+                        continue;
+                    }
+                }
+                //the bird crosses the ith obstacle successfully if the bird's height at x=position[i] is strictly greater than heights[i]
+                else   
+                {
+                    pos = position[i];
+                    i++;
+                }
+            }
+            
+            //printing the minimum number of clicks required to cross all the obstacles successfully
+            if(win)
+                System.out.println(ans);    
+         }
+    }
+}
+
+/*
+ * Example Input -
+ 
+   3
+   1 0
+   2
+   1
+   2 1
+   1 3
+   1 1
+   5 10
+   1 2 3 4 5
+   10 11 12 13 15
+   
+   Example Output -
+   
+   2
+   2
+   -1
+   
+ */