Skip to content

724. Find Pivot Index 👍

  • Time: $O(n)$
  • Space: $O(1)$
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
class Solution {
 public:
  int pivotIndex(vector<int>& nums) {
    const int sum = accumulate(nums.begin(), nums.end(), 0);
    int prefix = 0;

    for (int i = 0; i < nums.size(); ++i) {
      if (prefix == sum - prefix - nums[i])
        return i;
      prefix += nums[i];
    }

    return -1;
  }
};

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
class Solution {
  public int pivotIndex(int[] nums) {
    final int sum = Arrays.stream(nums).sum();
    int prefix = 0;

    for (int i = 0; i < nums.length; ++i) {
      if (prefix == sum - prefix - nums[i])
        return i;
      prefix += nums[i];
    }

    return -1;
  }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
class Solution:
  def pivotIndex(self, nums: list[int]) -> int:
    summ = sum(nums)
    prefix = 0

    for i, num in enumerate(nums):
      if prefix == summ - prefix - num:
        return i
      prefix += num

    return -1