jxustOJ 2388 最短区间（贪心，思维）

​​https://oj.ismdeep.com/problem?id=2388​​

分析：维护一个区间[l, i]，不断去重，每达到包含所有m种数就记录

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
#define d(x) cout << (x) << endl
using namespace std;
typedef long long ll;

const int N = 1e6 + 10;
const int M = 2020;
int a[N]; //原始数据
int b[M]; //记录区间[l, i]中每种数出现次数
int n, m;
int main()
{
    int ans = 0, res = 0, MIN = INF; //res代表出现过几种数
    scanf("%d%d", &n, &m);
    int l = 1;
    for (int i = 1; i <= n; i++)
    {
        scanf("%d", &a[i]);
        if (!a[i]) //跳过零
            continue;
        if (!b[a[i]]) //某种数第一次出现res++
            res++;
        b[a[i]]++; //记录每种数出现次数
        while (a[l] == 0)
            l++; //跳过零
        while (b[a[l]] > 1)     //如果在区间 l, i中出现过a[l]，去重
        {
            b[a[l]]--;          
            l++;                //右移l
            while (a[l] == 0)
                l++;
        }
        if (res == m)
            MIN = min(MIN, i - l + 1);
    }
    if (res != m)
        cout << -1 << endl;
    else
        cout << MIN << endl;
    return 0;
}