jxustOJ 2388 最短區間（貪心，思維）

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

#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]; //原始資料
int b[M]; //記錄區間[l, i]中每種數出現次數
int n, m;
int main()
{
    int ans = 0, res = 0, MIN = INF; //res代表出現過幾種數
    scanf("%d%d", &n, &m);
    int l = 1;
    for (int i = 1; i <= n; i++)
    {
        scanf("%d", &a[i]);
        if (!a[i]) //跳過零
            continue;
        if (!b[a[i]]) //某種數第一次出現res++
            res++;
        b[a[i]]++; //記錄每種數出現次數
        while (a[l] == 0)
            l++; //跳過零
        while (b[a[l]] > 1)     //如果在區間 l, i中出現過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;
}