知识点：模拟、字符串处理、哈希表

我的写法

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
using namespace std;
int ans;
string s, res, ss;
unordered_map<string, int> m;
int main() {
    getline(cin, s);
    for (int i = 0; s[i]; i ++ ) if(s[i] >= 'A' && s[i] <= 'Z') s[i] += 32;
    for (int i = 0; s[i]; i ++ ) {
        if((s[i] >='a' && s[i] <= 'z') || (s[i] >= '0' && s[i] <= '9')) ss += s[i];
        else if(ss != "") {
            m[ss] ++;
            if(m[ss] > ans || (m[ss] == ans && ss < res)) {
                ans = m[ss];
                res = ss;
            }
            ss = "";
        }
    }
    if(ss != "") {
        m[ss] ++;
        if(m[ss] > ans || (m[ss] == ans && ss < res)) ans = m[ss], res = ss;
    }
    cout << res << ' ' << ans << endl;
    return 0;
}

y总的写法

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
using namespace std;
int ans = -1;
string s, res;
unordered_map<string, int> m;
bool check(char c) {
    if(c >= 'A' && c <= 'Z') return true;
    if(c >= 'a' && c <= 'z') return true;
    if(c >= '0' && c <= '9') return true;
    return false;
}
char to_lower(char c) {
    if(c >= 'A' && c <= 'Z') return c + 32;
    return c;
}
int main() {
    getline(cin, s);
    for (int i = 0; s[i]; i ++ ) {
        if(check(s[i])) {
            string ss;
            int j = i;
            while(s[j] && check(s[j])) ss += to_lower(s[j ++ ]);
            m[ss] ++ ;
            i = j;
        }
    }
    for (auto x: m) {
        if(x.second > ans || (x.second == ans && x.first < res)) {
            ans = x.second;
            res = x.first;
        }
    }
    cout << res << ' ' << ans << endl;
    return 0;
}