codeforces--701C They Are Everywhere(尺取法)

cf 701C

题解

求包含所有出现过的元素的最短区间长度。

见 poj–3320 Jessica’s Reading Problem(尺取法)

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


int main(){

    int n;
    string s;

    cin >> n >> s;

    set<char> all;
    for(int i = 0; i < s.length(); ++i) all.insert(s[i]);
    int cnt = all.size();

    map<char, int> count;
    int L = 0, R = 0, num = 0;
    int ans = n;

    for(; ;){
        while(R < n && num < cnt){
            if(count[s[R++]]++ == 0) num++;
        }
        if(num < cnt) break;
        ans = min(ans, R - L);
        if(--count[s[L++]] == 0) num--;
    }

    cout << ans << endl;

    return 0;
}