3028. Ant on the Boundary

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.

Notes:

• There is an infinite space on both sides of the boundary.
• We check whether the ant is on the boundary only after it has moved |nums[i]| units. In other words, if the ant crosses the boundary during its movement, it does not count.

class Solution {
public:
    int returnToBoundaryCount(vector<int>& nums) {
        int res = 0, now = 0;
        for(auto& n : nums) {
            now += n;
            if(now == 0) res += 1;
        }
        return res;
    }
};