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Problem Description：
The task is simple: given any positive integer N, you are supposed to count the total number of 1's in the decimal form of the integers from 1 to N. For example, given N being 12, there are five 1's in 1, 10, 11, and 12.
Input Specification:
Each input file contains one test case which gives the positive N (≤230).
Output Specification:
For each test case, print the number of 1's in one line.
Sample Input:
代码语言：javascript复制12Sample Output:
代码语言：javascript复制5解题思路：
我一开始的思路就是暴力破解，无脑将1~N转换成字符串，然后无脑for-each来数字符'1'出现的次数，果不其然?直接TLE！30分只得22分。
AC代码： TLE代码：
代码语言：javascript复制#include <bits/stdc .h>
using namespace std;
int count1(int n) //用来数从1到n出现了几个1
{
int cnt = 0;
for(int i = 1; i <= n; i )
{
string temp = to_string(i);
for(auto it : temp)
{
if(it == '1')
{
cnt ;
}
}
}
return cnt;
}
int main()
{
int N;
cin >> N;
cout << count1(N) << endl;
return 0;
}
