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#include
#include
#include
#include
using namespace std; typedef long long ll; const int maxn = 1e6 + 10; int a[maxn]; ll segment_tree[3 * maxn]; void build_tree(int L, int R, int pos) { if(L == R) { segment_tree[pos] = 0; } else { int middle = (L + R) / 2; build_tree(L, middle, 2 * pos); build_tree(middle + 1, R, 2 * pos + 1); segment_tree[pos] = segment_tree[2 * pos] + segment_tree[2 * pos + 1]; } } ll query(int L, int R, int pos, int i, int j) { // R i L R j L if(i <= L and R <= j) { return segment_tree[pos]; } if(R < i or j < L) { return 0; } int mid = (L + R) / 2; return query(L, mid, 2 * pos, i, j) + query(mid + 1, R, 2 * pos + 1, i, j); } void update(int L, int R, int pos, int idx, int new_val) { if(L == R) { segment_tree[pos] += new_val; return; } int mid = (L + R) / 2; if(idx <= mid) { update(L, mid, 2 * pos, idx, new_val); } else { update(mid + 1, R, 2 * pos + 1, idx, new_val); } segment_tree[pos] = segment_tree[2 * pos] + segment_tree[2 * pos + 1]; } int main() { ios_base::sync_with_stdio(false); int n; cin >> n; for(int i = 0; i < n; i++) { cin >> a[i]; } build_tree(0, n - 1, 1); map
cnt; vector
freq(n, 0); for(int i = 0; i < n; i++) { cnt[a[i]]++; freq[i] = cnt[a[i]]; } map
cnt2; ll result = 0; for(int i = n - 1; i >= 0; i--) { result += query(0, n - 1, 1, 0, freq[i] - 1); cnt2[a[i]]++; update(0, n - 1, 1, cnt2[a[i]], 1); } cout << result << endl; return 0; }
Mark as private (unlisted)
for 30 minutes
for 6 hours
for 1 day
for 1 week
for 1 month
for 1 year
everlasting (like CCCP)