题解 | #计算某字符出现次数#

哈希表，极致占用内存，注意代码规范

#include <bits/stdc++.h>
using namespace std;
int main () {
	unordered_map<char, int>rec;
	string str;
	getline(cin, str);
	for (auto it : str) {
		rec[it]++;
	}
	char c;
	cin >> c;
	int sum = rec[c];
	if (c >= 'a' && c <= 'z') {
		sum += rec[c - 32];
	} 
	if (c >= 'A' && c <= 'Z'){
		sum += rec[c + 32];
	}
	cout << sum;
	return 0;
}