HDU 2665 Kth number (partition tree)

HDU 2665 Kth number (partition tree)

Idea: Divide tree template question.

For details, see the code:

 

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               #define Max(a,b) ((a)>(b)?(a):(b))#define Min(a,b) ((a)<(b)?(a):(b))using namespace std;typedef long long ll;typedef long double ld;const ld eps = 1e-9, PI = 3.1415926535897932384626433832795;const int mod = 1000000000 + 7;const int INF = 0x3f3f3f3f;// & 0x7FFFFFFFconst int seed = 131;const ll INF64 = ll(1e18);const int maxn = 1e5 + 10;int T,n,m;int tree[20][maxn];int sorted[maxn];int toleft[20][maxn];void build(int l, int r, int dep) { if(l == r) return ; int mid = (l + r) >> 1; int same = mid - l + 1; for(int i = l; i <= r; i++) { if(tree[dep][i] < sorted[mid]) same--; } int lpos = l; int rpos = mid + 1; for(int i = l; i <= r; i++) { if(tree[dep][i] < sorted[mid]) tree[dep+1][lpos++] = tree[dep][i]; else if(tree[dep][i] == sorted[mid] && same > 0) { tree[dep+1][lpos++] = tree[dep][i]; same--; } else tree[dep+1][rpos++] = tree[dep][i]; toleft[dep][i] = toleft[dep][l-1] + lpos - l; } build(l, mid, dep+1); build(mid+1, r, dep+1);}int query(int L, int R, int l, int r, int dep, int k) { if(l == r) return tree[dep][l]; int mid = (L + R) >> 1; int cnt = toleft[dep][r] - toleft[dep][l-1]; if(cnt >= k) { int newl = L + toleft[dep][l-1] - toleft[dep][L-1]; int newr = newl + cnt - 1; return query(L, mid, newl, newr, dep+1, k); } else { int newr = r + toleft[dep][R] - toleft[dep][r]; int newl = newr - (r - l - cnt); return query(mid+1, R, newl, newr, dep+1, k - cnt); }}int l, r, k;int main() { scanf("%d",&T); while(T--) { memset(tree, 0, sizeof(tree)); scanf("%d%d",&n,&m); for(int i = 1; i <= n; i++) { scanf("%d",&tree[0][i]); sorted[i] = tree[0][i]; } sort(sorted+1, sorted+n+1); build(1, n, 0); while(m--) { scanf("%d%d%d",&l, &r, &k); printf("%d\n",query(1, n, l, r, 0, k)); } } return 0;}