// Package q1582 implements a solution for https://leetcode.com/problems/special-positions-in-a-binary-matrix/
package q1582

func numSpecial(mat [][]int) int {
	hPos := make([]int, len(mat))
	vPos := make([]int, len(mat[0]))
	for i := range vPos {
		vPos[i] = -1
	}

	for row := range mat {
		hPos[row] = -1
		for col, val := range mat[row] {
			if val == 1 {
				if hPos[row] >= 0 {
					hPos[row] = -2
				} else if hPos[row] == -1 {
					hPos[row] = col
				}

				if vPos[col] >= 0 {
					vPos[col] = -2
				} else if vPos[col] == -1 {
					vPos[col] = row
				}
			}
		}
	}

	pairs := 0
	for i := range hPos {
		if hPos[i] >= 0 && vPos[hPos[i]] == i {
			pairs++
		}
	}
	return pairs
}

var _ = numSpecial