题目链接

https://atcoder.jp/contests/abc345/tasks/abc345_c

代码

#include<bits/stdc++.h>
using namespace std;

typedef long long LL;

LL C(LL n) {
    LL res = n * (n - 1) / 2;
    return res;
}

int main() {
    string s;
    cin >> s;

    unordered_map<char, int> mp;
    for(int i = 0; i < s.size(); i ++) {
        mp[s[i]] ++;
    }

    bool flag = false;

    LL X = C(s.size());
    for(auto& [u, v] : mp) {
        X -= C(v);
        if(v > 1) flag = true;
    }

    if(flag == true) cout << X + 1 << '\n';
    else cout << X << '\n';

    return 0;
}