shiva kumar - 1 year ago 57

Python Question

I was solving the question from the website CodeChef.

I found this question:

Some programming contest problems are really tricky: not only do they

require a different output format from what you might have expected,

but also the sample output does not show the difference. For an

example, let us look at permutations. A permutation of the integers 1

to n is an ordering of these integers. So the natural way to represent

a permutation is to list the integers in this order. With n = 5, a

permutation might look like 2, 3, 4, 5, 1. However, there is another

possibility of representing a permutation: You create a list of

numbers where the i-th number is the position of the integer i in the

permutation. Let us call this second possibility an inverse

permutation. The inverse permutation for the sequence above is 5, 1,

2, 3, 4. An ambiguous permutation is a permutation which cannot be

distinguished from its inverse permutation. The permutation 1, 4, 3, 2

for example is ambiguous, because its inverse permutation is the same.

To get rid of such annoying sample test cases, you have to write a

program which detects if a given permutation is ambiguous or not.

Input Specification

The input contains several test cases. The first line of each test

case contains an integer n (1 ≤ n ≤ 100000). Then a permutation of the

integers 1 to n follows in the next line. There is exactly one space

character between consecutive integers. You can assume that every

integer between 1 and n appears exactly once in the permutation. The

last test case is followed by a zero.

Output Specification

For each test case output whether the permutation is ambiguous or not.

Adhere to the format shown in the sample output.

Sample Input

4 1 4 3 2 5 2 3 4 5 1 1 1 0 Sample Output

ambiguous not ambiguous ambiguous

I post the following python code but they said my answer is wrong

can someone help me where is the mistake in my logic?

`def main():`

T=int(input())

result=[]

while(T!=0):

list=[]

list1=[]

y=0

value=raw_input().split(' ')

for x in value:

list.append(int(x))

for x in list:

y+=1

x=list.index(y)+1

list1.append(x)

if(list==list1):

result.append("ambiguous")

else:

result.append("non-ambiguous")

T=int(input())

for a in result:

print a

main()

Answer Source

For this kind of things, before doubting your code it's better to double-check that the way you handle input and output match what's expected.

I know how silly you feel when you realize you fail the tests despite a correct algorithm, for something like using the string `non-ambiguous`

instead of the expected `not ambiguous`

.