Maximum Trailing Zeros in a Cornered Path LeetCode solution in C++

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array<int, 2> operator+(const array<int, 2> &l, const array<int, 2> &r) {
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  return {l[0] + r[0], l[1] + r[1]};
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}
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array<int, 2> operator-(const array<int, 2> &l, const array<int, 2> &r) {
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  return {l[0] - r[0], l[1] - r[1]};
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}
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int pairs(const array<int, 2> &p) {
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  return min(p[0], p[1]);
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}
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class Solution {
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 public:
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  int factors(int i, int f) {
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    return i % f ? 0 : 1 + factors(i / f, f);
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  }
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  int maxTrailingZeros(vector<vector<int>> &grid) {
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    int m = grid.size(), n = grid[0].size(), res = 0;
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    vector<vector<array<int, 2>>> h(m, vector<array<int, 2>>(n + 1)),
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        v(m + 1, vector<array<int, 2>>(n));
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    for (int i = 0; i < m; ++i)
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      for (int j = 0; j < n; ++j) {
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        array<int, 2> f25 = {factors(grid[i][j], 2), factors(grid[i][j], 5)};
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        v[i + 1][j] = v[i][j] + f25;
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        h[i][j + 1] = h[i][j] + f25;
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      }
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    for (int i = 0; i < m; ++i)
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      for (int j = 0; j < n; ++j) {
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        auto v1 = v[i + 1][j], v2 = v[m][j] - v[i][j];
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        auto h1 = h[i][j], h2 = h[i][n] - h[i][j + 1];
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        res = max({res, pairs(v1 + h1), pairs(v1 + h2), pairs(v2 + h1), pairs(v2 + h2)});
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      }
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    return res;
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  }
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};