static ArrayList < Pair > findSubArrays ( int [ ] arr , int n ) {
  HashMap < Integer , ArrayList < Integer >> map = new HashMap < > ( ) ;
  ArrayList < Pair > out = new ArrayList < > ( ) ;
  int sum = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    sum += arr [ i ] ;
    if ( sum == 0 ) out . add ( new Pair ( 0 , i ) ) ;
    ArrayList < Integer > al = new ArrayList < > ( ) ;
    if ( map . containsKey ( sum ) ) {
      al = map . get ( sum ) ;
      for ( int it = 0 ;
      it < al . size ( ) ;
      it ++ ) {
        out . add ( new Pair ( al . get ( it ) + 1 , i ) ) ;
      }
    }
    al . add ( i ) ;
    map . put ( sum , al ) ;
  }
  return out ;
}

static ArrayList < Pair > findSubArrays ( int [ ] arr , int n ) { HashMap < Integer , ArrayList < Integer > > map = new HashMap < > ( ) ; ArrayList < Pair > out = new ArrayList < > ( ) ; int sum = 0 ; for ( int i = 0 ; i < n ; i ++ ) { sum += arr [ i ] ; if ( sum == 0 ) out . add ( new Pair ( 0 , i ) ) ; ArrayList < Integer > al = new ArrayList < > ( ) ; if ( map . containsKey ( sum ) ) { al = map . get ( sum ) ; for ( int it = 0 ; it < al . size ( ) ; it ++ ) { out . add ( new Pair ( al . get ( it ) + 1 , i ) ) ; } } al . add ( i ) ; map . put ( sum , al ) ; } return out ; }
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