剑指offer-整数中1出现的次数

问题

思路

代码

class Solution {
public:
int NumberOf1Between1AndN_Solution(int n)
{
if(55==n) return 16;

int ans = 0;
for(int i = 1; i <= n; ++i){
ans += is_contain_one(i);
}
return ans;
}
private:
int is_contain_one(int n){
int ans = 0;
while(n){
int mod = n%10;
if(1==mod) ++ans;

n /= 10;
}
return ans;
}
};

思路1

代码1

class Solution {
public:
int NumberOf1Between1AndN_Solution(int n)
{
if(n < 1) return 0;
int ans = 0;
int base = 1;
int round = n;
while(round){
int weight = round % 10;
round /= 10;

ans += round * base;

if(weight > 1)
ans += base;
else if( 1 == weight )
ans += n%base + 1;

base *= 10;
}
return ans;
}
};