题解 | #整数中1出现的次数#

package main


/**
 * 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 n int整型
 * @return int整型
 */
func NumberOf1Between1AndN_Solution( n int ) int {
    // write code here
    base := 1
    res := 0

    for base <= n {
        b := n%base
        a := n/base
        cur := a%10
        a = a/10
        if cur > 1 {
            res += (a+1) * base
        } else if cur == 1 {
            res += (a*base+b+1)
        }else {
            res += a*base
        }
        base = base * 10
    }
    return res
}