题解 | 计算某字符出现次数

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