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  1.  
  2. import java.util.HashMap;
  3.  
  4. public class Main {
  5.     public static void main(String[] args) {
  6.         int  n = 6;
  7. 		int[] P = new int[]{0,6,7,2,100,10};
  8.  
  9.  
  10.         long c = 0;
  11.         HashMap<Integer, Integer> freq = new HashMap<>();
  12.  
  13.  
  14.         if (n > 0) {
  15.             freq.put(P[0], 1);
  16.         }
  17.  
  18.  
  19.         for (int j = 1; j < n; j++) {
  20.             int rhs = P[j] - j;
  21.             c = c + freq.getOrDefault(rhs, 0);
  22.  
  23.             int prevValue= P[j - 1] - j + 1;
  24.             freq.put(prevValue, freq.getOrDefault(prevValue, 0) + 1);
  25.         }
  26.  
  27.         System.out.println(c);
  28.  
  29.     }
  30. }
  31.  
Success #stdin #stdout 0.07s 54552KB
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https://ideone.com/yNrmvx
language:
Java (HotSpot 12)
created:
7 hours ago
visibility:
public

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