codeforces 190D Non-Secret Cypher 双指针

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给定长度为n的数组a，给定k，问有多少个子数组，其中至少包含着有k个相同的数字

双指针经典题目，注意先要离散，然后注意m是1的情况

#include <iostream>#include <cstring>#include <cstdio>#include <algorithm>#include <map>#define rep(i, j, k) for(int i = j; i <= k; i++)#define maxn 1000009#define ll long longusing namespace std;int n, m, a[maxn], c[maxn], now = 0, cnt = 0;int cunt[maxn];map <int, int> mp;ll ans = 0;int main (){cin >> n >> m;rep (i, 1, n)cin >> a[i], c[i] = a[i];sort (c + 1, c + 1 + n);c[0] = c[1] - 1;cnt = 0;rep (i, 1, n)if (c[i] != c[i - 1])mp[c[i]] = ++cnt;rep (i, 1, n)a[i] = mp[a[i]];//rep (i, 1, n) printf ("%d %d\n", i, a[i]);int r = 1;cunt[a[1]]++;if (m == 1)now++;rep (l, 1, n){while (now == 0 && r < n){r++;cunt[a[r]]++;if (cunt[a[r]] >= m)now++;}if (now)ans += 1LL * n - 1LL * r + 1LL;cunt[a[l]]--;if (cunt[a[l]] == m - 1)now--;}cout << ans << endl;}

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