题解 | #填充数组#

其实就是简单结合排列组合和大数计算

package main
import "math/big"

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 *
 * @param a int整型一维数组
 * @param k int整型
 * @return int整型
 */
func FillArray(a []int, k int) int {
	// write code here
	startNum, count := 1, 0
	res := int64(1)
	for i := 0; i < len(a); i++ {
		if a[i] == 0 {
			count++
			continue
		}
		if count != 0 {
			res = (res * getSection(a[i]-startNum, count)) % 1000000007
		}
		startNum = a[i]
		count = 0
	}
	if count != 0 {
		res = (res * getSection(k-startNum, count)) % 1000000007
	}
	return int(res)
}

func getSection(inter, num int) int64 {
	if num == 0 || inter < 0 {
		return 0
	}
	if inter == 0 {
		return 1
	}
	res := big.NewInt(1)
	for i := num + inter; i > num; i-- {
		res.Mul(res, big.NewInt(int64(i)))
	}
	for i := 1; i <= inter; i++ {
		res.Div(res, big.NewInt(int64(i)))
	}
	return res.Mod(res, big.NewInt(1000000007)).Int64()
}