You are in a party of N people, where only one person is known to everyone. Such a person may be present in the party, if yes, (s)he doesn’t know anyone in the party. Your task is to find the stranger (celebrity) in party.
You will be given a square matrix M where if an element of row i and column j is set to 1 it means ith person knows jth person. You need to complete the function getId() which finds the id of the celebrity if present else return -1. The function getId() takes two arguments, the square matrix M and its size N.
Here, M[i][i] will be equal to zero.
Note: Expected time complexity is O(N) with constant extra space.
The first line of input contains an element T denoting the number of test cases. Then T test cases follow. Each test case consist of 2 lines. The first line of each test case contains a number denoting the size of the matrix M. Then in the next line are space separated values of the matrix M.
For each test case output will be the id of the celebrity if present (0 based index). Else -1 will be printed.
The task is to complete the function getId() which returns the Id of celebrity if present, else -1.
1 <= T <= 50
2 <= N <= 501
0 <= M <= 1
0 1 0 0 0 0 0 1 0
0 1 1 0
For the above test case the matrix will look like
0 1 0
0 0 0
0 1 0
Here, the celebrity is the person with index 1 ie id 1
The matrix will look like
Here, there is no such person who is a celebrity (a celebrity should know no one).
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