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 #include #include #include #include #define rep(i, j, k) for(int i = j; i <= k; i++) #define maxn 1000009 #define ll long long using namespace std; int n, m, a[maxn], c[maxn], now = 0, cnt = 0; int cunt[maxn]; map 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; }
