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