P1168 中位数

离散化，线段树 #include using namespace std; const int N = 1e5 + 7; int a[N], tree[N << 4], hs[N]; void add(int x, int i, int l, int r){ tree[i] ++; if(l == r) return; int mid = (l + r) >> 1; if(x <= mid) add(x, i << 1, l, mid); else add(x, i << 1 | 1, mid + 1, r); } int query(int m, int i, int l, int r){ if(l == r) return hs[l]; int mid = (l + r) >> 1; if(tree[i << 1] >= m) return query(m, i << 1, l, mid); else return query(m - tree[i << 1], i << 1 | 1,mid + 1, r); } int main(){ int n; scanf("%d", &n); for(int i = 1;i <= n;i ++) scanf("%d", &a[i]), hs[i] = a[i]; sort(hs + 1, hs + n + 1); int t = unique(hs + 1, hs + n + 1) - hs - 1; int p = lower_bound(hs + 1, hs + t + 1, a[1]) - hs; add(p, 1, 1, t); printf("%d\n", query(1, 1, 1, t)); for(int i = 3;i <= n;i += 2){ p = lower_bound(hs + 1, hs + t + 1, a[i]) - hs; add(p, 1, 1, t); p = lower_bound(hs + 1, hs + t + 1, a[i - 1]) - hs; add(p, 1, 1, t); printf("%d\n", query(i/2 + 1, 1, 1, t)); } return 0; }