Problem Description
An ant is on a boundary. It sometimes goes left and sometimes right. You are given an array of non-zero integers nums. The ant starts reading nums from the first element of it to its end. At each step, it moves according to the value of the current element:
- If nums[i] < 0, it moves left by -nums[i] units.
- If nums[i] > 0, it moves right by nums[i] units.
Return the number of times the ant returns to the boundary.
Key Insights
- The ant's position changes based on the cumulative sum of the values in the nums array.
- The boundary is defined as the point where the ant's position equals zero.
- You need to track the ant's position after each move and count how many times it equals zero.
Space and Time Complexity
Time Complexity: O(n)
Space Complexity: O(1)
Solution
To solve the problem, we can use a simple simulation approach. We maintain a variable to keep track of the ant's current position, initialized to zero. As we iterate through the nums array, we update the position based on the current value. After each move, we check if the position equals zero, indicating the ant has returned to the boundary. We need to count these occurrences.
The primary data structure used is a simple integer to track the position of the ant, and the algorithm runs in linear time as we only need a single pass through the nums array.