Counting Problems P1980 (int, string, stringstream)

Title Description

Calculate the range of  1  to  all integers n, the digital x (0 ≤ x ≤ 9) were appeared many times? For example, in the  1  to  1 1, i.e. in  1,2,3,4,5,6,7,8,9,10,11  , the number  1  appears  four times.

Input Format

Two integers  n-, X  , separated by a space between.

Output Format

1  integer representing  the number of times x appears.

Sample input and output

Entry 

11 1

Export 

4

Description / Tips

For  . 1 0 0 % of the data, . 1 ≤ n- ≤ . 1 , 0 0 0 , 0 0 0 , 0 ≤ X ≤ . 9.

Code:

#include<cstdio>
#include<iostream>
#include<sstream>
#include<algorithm>
using namespace std;
int main(){
    int x,n;
    scanf("%d %d",&n,&x);
    int sum=0;
    stringstream ss;
    string s;
    for(int i=1;i<=n;i++){
        ss<<i; 
    }
    s=ss.str();    
    printf("%d",count(s.begin(), s.end(), x + '0'));
}

Encounter problems:

1. [Error] stray '\ 243'in program Cause: The compiler encounters illegal characters unrecognized when compiling the source file

2. [Error] 'to_string' was not declared in this scope the wrong reasons: to_string is c ++ 11 inside, but no dev c ++ 11 environment, we only need to find the Tools -> compiler option to add -std = c + +11
3. 
4. stringstream use

5. #include<cstdio> 
   #include<iostream>
   #include<string>
   #include<sstream> //stringstream 所需的头文件
   using namespace std;
   int main(){
       string s="35";
       string tem;
       stringstream ss;
       int a;
       ss<<s;//将 s 读入字符串流中
       ss>>a;//把字符串转为数值
       tem=ss.str();//stringstream 型不能直接输出,也不支持迭代器,需要利用 stringstream 类的成员函数str()才能把它当成普通字符串来用
   }