sudoku - sorted.go

     1  package sudoku
     2  
     3  // Sorted is a Constraint that requires the numbers to be ordered lowest to highest.
     4  type Sorted []int
     5  
     6  // Constrain implements the Constraing interface.
     7  func (s Sorted) Constrain(su *Sudoku, pos int, marked []bool) bool {
     8  	sp := slicePos([]int(s), pos)
     9  	if sp == -1 {
    10  		return true
    11  	}
    12  	min := 1
    13  	nums := make([]int, len(s))
    14  	for n, p := range s {
    15  		nums[n] = su.Pos(p)
    16  	}
    17  	f := false
    18  	for i := 0; i < sp; i++ {
    19  		if mp := su.Pos(s[i]); mp == 0 {
    20  			min++
    21  		} else if mp+1 > min {
    22  			min = mp + 1
    23  		} else if f {
    24  			return false
    25  		}
    26  		f = true
    27  	}
    28  	max := su.Chars()
    29  	f = false
    30  	for i := len(s) - 1; i > sp; i-- {
    31  		if mp := su.Pos(s[i]); mp == 0 {
    32  			max--
    33  		} else if mp-1 < max {
    34  			max = mp - 1
    35  		} else if f {
    36  			return false
    37  		}
    38  		f = true
    39  	}
    40  	if max-min < 0 {
    41  		return false
    42  	}
    43  	for i := 1; i < min; i++ {
    44  		marked[i] = true
    45  	}
    46  	for i := su.Chars(); i > max; i-- {
    47  		marked[i] = true
    48  	}
    49  	return true
    50  }