好串的数目 参考代码

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

typedef long long LL;
const LL MOD = 1000000007;
const int maxn = 100000 + 100;
int n, nxt, idx;
LL ans;
char str[maxn];
LL len[maxn];

int findNxt(int idx) {
    for (int i = idx + 1; i < n; ++i) {
        if (str[i] != str[i - 1] && str[i] != str[i - 1] + 1) {
            return i;
        }
    }
    return n;
}

int main() {
#ifdef ExRoc
    freopen("test.txt", "r", stdin);
#endif // ExRoc

    cin >> str;
    n = strlen(str);
    for (int i = 0; i < n; i = nxt) {
        nxt = findNxt(i);
        len[idx] = nxt - i;
        ans += len[idx] * (len[idx] + 1) / 2;
        ++idx;
    }
    for (int i = 1; i < idx; ++i) {
        ans += len[i] * len[i - 1];
    }
    cout << ans << endl;

    return 0;
}