Added for 18 Jan

GeeksForGeeks/18-1-24/GFG.java

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+//{ Driver Code Starts
+//Initial Template for Java
+
+import java.util.*;
+import java.io.*;
+
+class GFG {
+	public static void main (String[] args)throws IOException {
+
+		BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
+		PrintWriter out=new PrintWriter(System.out);
+		int t = Integer.parseInt(in.readLine().trim());
+        while(t-- > 0)
+        {
+            int n = Integer.parseInt(in.readLine().trim());
+            String s[]=in.readLine().trim().split(" ");
+
+            int gallery[] = new int[n];
+            for(int i=0; i<n; i++)
+                gallery[i] = Integer.parseInt(s[i]);
+            Solution T = new Solution();
+            out.println(T.min_sprinklers(gallery,n));
+        }
+		out.close();
+
+	}
+}
+
+
+
+
+
+// } Driver Code Ends
+
+
+//User function Template for Java
+
+class pair 
+{
+    int x;
+    int y;
+    pair(int x1, int y1)
+    {
+        x = x1;
+        y = y1;
+    }
+}
+
+
+class Solution
+{
+    int min_sprinklers(int arr[], int N)
+    {
+        ArrayList<pair> V = new ArrayList<pair>();
+
+        // Traverse the array arr[]
+        for (int i = 0; i < N; i++) 
+        {
+            if (arr[i] > -1) 
+            {
+                V.add(new pair(i - arr[i], i + arr[i]));
+            }
+        }
+
+        Collections.sort(V, new Comparator<pair>()  {
+            @Override public int compare(pair p1, pair p2)
+            {
+                return p1.x - p2.x;
+            }});
+
+        int maxRight = 0;
+        int res = 0;
+        int i = 0;
+
+        while (maxRight < N) 
+        {
+            if (i == V.size() || V.get(i).x > maxRight)
+                return -1;
+
+            int currMax = V.get(i).y;
+
+            while (i + 1 < V.size() && V.get(i + 1).x <= maxRight) 
+            {
+                i++;
+                currMax = Math.max(currMax, V.get(i).y);
+            }
+
+            if (currMax < maxRight)
+                return -1;
+
+            res++;
+            maxRight = currMax + 1;
+            i++;
+        }
+
+        return res;
+    }
+}

GeeksForGeeks/18-1-24/README.md

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+Time complexity - O(n * logn)
+Space complexity - O(n)

LeetCode/18-1-24/README.md

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+Time complexity - O(n)
+Space complexity - O(1)

LeetCode/18-1-24/Solution.java

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+class Solution
+{
+    // using 1d DP, but actually not
+    public int climbStairs(int n)
+    {
+        // declaring  two variables to store the count
+        int prev = 1;
+        int prev2 = 1;
+        int curr = 0;
+        // Running for loop to count all possible ways
+        for (int i = 2; i <= n; i++)
+        {
+            curr = prev + prev2;
+            prev2 = prev;
+            prev = curr;
+        }
+        return prev;
+    }
+}