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| // @Title: 重新排序得到 2 的幂 (Reordered Power of 2)
// @Author: 15816537946@163.com
// @Date: 2021-10-28 21:59:06
// @Runtime: 24 ms
// @Memory: 2 MB
func isPowerOf2(n int) bool {
return n&(n-1) == 0
}
func reorderedPowerOf2(n int) bool {
nums := []byte(strconv.Itoa(n))
sort.Slice(nums, func(i, j int) bool { return nums[i] < nums[j] })
m := len(nums)
vis := make([]bool, m) // 用于标记回溯
var backtrack func(int, int) bool
// 通过回溯拿到全排列
backtrack = func(idx, num int) bool {
if idx == m {
return isPowerOf2(num)
}
for i, ch := range nums {
// 不能有前导0
if num == 0 && ch == '0' || vis[i] || i > 0 && !vis[i-1] && ch == nums[i-1] {
continue
}
vis[i] = true
if backtrack(idx+1, num*10+int(ch-'0')) {
return true
}
vis[i] = false
}
return false
}
return backtrack(0, 0)
}
|