func Euler041() int {
//process 7 digit pandigitals
p7d := make([]int, 0, 5040) //7!
for v := range utils.Perm(utils.Numerals[1:8]) {
n, _ := strconv.Atoi(v)
p7d = append(p7d, n)
}
sort.Sort(sort.Reverse(sort.IntSlice(p7d)))
for i := 0; i < 5040; i++ {
if utils.IsPrime(p7d[i]) {
return p7d[i]
}
}
//process 4 digit pandigitals
p4d := make([]int, 0, 24) //4!
for v := range utils.Perm(utils.Numerals[1:5]) {
n, _ := strconv.Atoi(v)
p4d = append(p4d, n)
}
sort.Sort(sort.Reverse(sort.IntSlice(p4d)))
for i := 0; i < 5040; i++ {
if utils.IsPrime(p4d[i]) {
return p4d[i]
}
}
return -1
}
func GetPermutations(n uint64) map[uint64]bool {
pMap := make(map[uint64]bool, 24)
sp := utils.Perm(strconv.FormatUint(n, 10))
for s := range sp {
np, _ := strconv.ParseUint(s, 10, 64)
pMap[np] = true
}
return pMap
}
func Euler024(pNum int) string {
i := 1
for v := range utils.Perm(utils.Numerals) {
if i == pNum {
return v
}
i++
}
return ""
}
/* solution:
since d4d5d6 must be divisible by 5: d6:=is in {0,5}
since d6d7d8 must be divisible by 11 d6 can not be 0 (that would leave only 011,022 etc that break the pandigital condition)
d4 must be even
will brute-force the rest
*/
func Euler043() int {
s := 0
for p := range utils.Perm(utils.Numerals) {
if n, _ := strconv.Atoi(p[7:10]); n%17 != 0 {
continue
} else if n, _ := strconv.Atoi(p[6:9]); n%13 != 0 {
continue
} else if n, _ := strconv.Atoi(p[5:8]); n%11 != 0 {
continue
} else if n, _ := strconv.Atoi(p[4:7]); n%7 != 0 {
continue
} else if p[5:6] != "5" {
continue
} else if n, _ := strconv.Atoi(p[1:4]); n%2 != 0 {
continue
} else if n, _ := strconv.Atoi(p[2:5]); n%3 != 0 {
continue
}
n, _ := strconv.Atoi(p)
s += n
}
return s
}