Codeforces Round #364 (Div. 2) C. They Are Everywhere (尺取法）

要维护区间内字符数为定值，求最小的满足条件的区间典型的双指针。

#include <cstdio>#include <iostream>#include <cstring>#include <set>#include <map>using namespace std;#define pr(x) cout << #x << ": " << x << "  " #define pl(x) cout << #x << ": " << x << endl;struct jibancanyang{    int n, t;    string str;    void two() {        int l = 0, r = 0;        map<char, int> st;        int ret = int(1e9);        while (l < n) {            while (r < n && (int)st.size() < t) {                st[str[r++]]++;            }            if (t <= (int)st.size()) ret = min(ret, r - l);            else break;            st[str[l]]--;            if (st[str[l]] == 0) st.erase(str[l]);            l++;        }        cout << ret << endl;    }    void run() {        cin >> n >> str;        set<char> st;        for (int i = 0; i < (int)str.size(); i++) {            st.insert(str[i]);        }        t = st.size();        two();    }}ac;int main(){#ifdef LOCAL    freopen("in.txt", "r", stdin);    //freopen("out.txt", "w", stdout);#endif    ac.run();    return 0;}