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2 years ago
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
/**
*
*
* 2019-11-23
* @param y
* @return
*/
string convertNumToStr(int y) {
string res;
stringstream ss; // 定义流ss
ss << y; // 将数字a转化成流ss
ss >> res; // 将流ss转化成字符串
return res;
}
// 一题多解知识点:数字转字符串,字符串的遍历
int main() {
ll a, b, s = 0;
cin >> a >> b;
for (ll y = a; y <= b; y++) {
string str = convertNumToStr(y);
for (auto ch : str)//ch依次取的是str里面的字符,直到取完为止
{
if (ch == '2') {
s++;
}
}
}
cout << s << endl;
return 0;
}