// Package q3212 implements a solution for https://leetcode.com/problems/count-submatrices-with-equal-frequency-of-x-and-y/
package q3212

type State struct {
	x, y, dot uint32
}

func (s *State) Add(another *State) {
	s.x += another.x
	s.y += another.y
	s.dot += another.dot
}

func (s *State) Sub(another *State) {
	s.x -= another.x
	s.y -= another.y
	s.dot -= another.dot
}

func numberOfSubmatrices(grid [][]byte) int {
	cntPrev, cntCur := make([]State, len(grid[0])), make([]State, len(grid[0]))

	submatrices := 0
	for row := range grid {
		for col := range grid[0] {
			st := State{}
			switch grid[row][col] {
			case 'X':
				st.x = 1
			case 'Y':
				st.y = 1
			case '.':
				st.dot = 1
			}

			cntCur[col] = st
			cntCur[col].Add(&cntPrev[col])
			if col > 0 {
				cntCur[col].Add(&cntCur[col-1])
				cntCur[col].Sub(&cntPrev[col-1])
			}

			if cntCur[col].x > 0 && cntCur[col].y == cntCur[col].x {
				submatrices++
			}
		}
		cntPrev, cntCur = cntCur, cntPrev
	}
	return submatrices
}

var _ = numberOfSubmatrices