Given a string which consists of either ‘.’ or any number. A ‘.’ in the string means that the cell is empty and if there is a number in any cell, it means one can move steps to right or left within the string.
The task is to check if any cell in the string can be visited more than once. If so, print YES otherwise print NO.
Input : str = ".2...2.." Output: YES The fourth cell can be visited twice. One way to reach the fourth cell is from 2nd cell by moving 2 steps to right and another way to reach fourth cell is by moving 2 steps left from cell 6. Input : str = ".2...1" Output: NO None of the cells in the given string can be visited more than once.
The idea is to take an array visited to keep track of the number of times i-th cell of the string can be visited. Now traverse the string and check if the current character is a ‘.’ or a number . If the current character is a ‘.’ then do nothing otherwise if it is a number then increase the count of visits in the visited array within the range [i-x, i+x] by 1.
Finally, traverse the visited array and check if any cell is visited more than once.
Below is the implementation of the above approach:
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