Check if an Array is a permutation of numbers from 1 to N : Set 2 | Function to check if an array represents a permutation or not ; Counting the frequency ; Check if each frequency is 1 only ; Driver code
def permutation ( arr , N ) : NEW_LINE INDENT hash = [ 0 ] * ( N + 1 ) ; NEW_LINE for i in range ( N ) : NEW_LINE INDENT hash [ arr [ i ] ] += 1 ; NEW_LINE DEDENT for i in range ( 1 , N + 1 ) : NEW_LINE INDENT if ( hash [ i ] != 1 ) : NEW_LINE INDENT return " No " ; NEW_LINE DEDENT DEDENT return " Yes " ; NEW_LINE DEDENT if __name__ == " _ _ main _ _ " : NEW_LINE INDENT arr = [ 1 , 1 , 5 , 5 , 3 ] ; NEW_LINE n = len ( arr ) ; NEW_LINE print ( permutation ( arr , n ) ) ; NEW_LINE DEDENT