# 548. Split Array with Equal Sum

• Time: $O(n^2)$
• Space: $O(n)$
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 class Solution { public: bool splitArray(vector& nums) { const int n = nums.size(); if (n < 7) return false; vector prefix(n); partial_sum(nums.begin(), nums.end(), prefix.begin()); for (int j = 3; j < n - 3; ++j) { unordered_set seen; for (int i = 1; i < j - 1; ++i) if (prefix[i - 1] == prefix[j - 1] - prefix[i]) seen.insert(prefix[i - 1]); for (int k = j + 2; k < n - 1; ++k) if (prefix[n - 1] - prefix[k] == prefix[k - 1] - prefix[j] && seen.count(prefix[k - 1] - prefix[j])) return true; } return false; } }; 
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 class Solution { public boolean splitArray(int[] nums) { final int n = nums.length; if (n < 7) return false; int[] prefix = new int[n]; for (int i = 0; i < n; ++i) prefix[i] = i == 0 ? nums[0] : prefix[i - 1] + nums[i]; for (int j = 3; j < n - 3; ++j) { HashSet seen = new HashSet<>(); for (int i = 1; i < j - 1; ++i) if (prefix[i - 1] == prefix[j - 1] - prefix[i]) seen.add(prefix[i - 1]); for (int k = j + 2; k < n - 1; ++k) if (prefix[n - 1] - prefix[k] == prefix[k - 1] - prefix[j] && seen.contains(prefix[k - 1] - prefix[j])) return true; } return false; } }