TapeEquilibrium (누적합 + 이항)

- 길이 N(≥2)인 정수 배열 A가 주어짐.
- 0 < P < N 인 모든 분할점 P에 대해,
  왼쪽 합 S_left = A[0] + ... + A[P-1]
  오른쪽 합 S_right = A[P] + ... + A[N-1]
  의 차이 |S_left - S_right| 를 계산할 수 있다.
- 가능한 분할 중 최소 차이를 반환하라.

public class TapeEquilibrium
{
    public int solution(int[] A)
    {
        long total = 0;
 
        foreach (int num in A)
        {
            total += num;
        }
 
        // 이항 과정
        // total = S_left + S_right
        // -S_right = S_left + -total
        // S_right = -S_left + total
        // S_right = total - S_left
 
        long leftSum = 0;
        long minDiff = long.MaxValue;
 
        for (int i = 0; i < A.Length - 1; i++)
        {
            leftSum += A[i];
            long rightSum = total - leftSum;
 
            long diff = Math.Abs(leftSum - rightSum);
 
            if (diff < minDiff)
                minDiff = diff;
        }
 
 
        return (int)minDiff;
    }
}