first commit

J02027 - KHOẢNG CÁCH NHỎ HƠN K.java

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+import java.util.*;
+import java.io.*;
+
+public class Main {
+    static int uppper_bound(int l, int r, int[] a, int x){
+        if(l>r) return l;
+        int mid = (l+r)/2;
+        if(a[mid] > x) return uppper_bound(l, mid - 1 , a, x);
+        return uppper_bound(mid + 1, r, a, x);
+    }
+    public static void main(String[] args) throws IOException, ClassNotFoundException {
+        // Scanner sc = new Scanner(new File("ONLINE.in"));
+        Scanner sc = new Scanner(System.in);
+        int t = sc.nextInt();
+        while(t-->0){
+            int n = sc.nextInt(), k = sc.nextInt();
+            int[] a = new int[n];
+            for(int i=0;i<n;i++) a[i]=sc.nextInt();
+            Arrays.sort(a);
+            long sum = 0;
+            for(int i=1;i<n;i++){
+                int index = uppper_bound(0, i-1, a, a[i]-k);
+                sum += (long)(i - index);
+            }
+            System.out.println(sum);
+        }
+    }
+}