如题，这是一个模板。。。
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdio> 5 #include <cctype> 6 #include <cmath> 7 8 inline void read(int & x) 9 { 10 x = 0; 11 int k = 1; 12 char c = getchar(); 13 while (!isdigit(c)) 14 if (c == '-') c = getchar(), k = -1; 15 else c = getchar(); 16 while (isdigit(c)) 17 x = (x << 1) + (x << 3) + (c ^ 48), 18 c = getchar(); 19 x *= k; 20 } 21 22 const int MAXN = 202020; 23 24 struct sgt 25 { 26 int l, r, w; 27 }t[MAXN << 5]; 28 29 int n, m, id = 0, cnt = 0, L, R, K; 30 int root[MAXN], a[MAXN], b[MAXN]; 31 32 inline int Lsh(int x) { return std::lower_bound(a + 1, a + cnt + 1, x) - a; } 33 34 void Pushup(int u) 35 { 36 t[u].w = t[t[u].l].w + t[t[u].r].w; 37 } 38 39 void Build(int u, int l, int r) 40 { 41 if (l == r) 42 { 43 t[u].l = -1; 44 t[u].r = -1; 45 t[u].w = 0; 46 return; 47 } 48 t[u].l = ++id; 49 t[u].r = ++id; 50 int mid = (l + r) >> 1; 51 Build(t[u].l, l, mid); 52 Build(t[u].r, mid + 1, r); 53 Pushup(u); 54 } 55 56 int Add(int u, int l, int r, int k) 57 { 58 int cur = ++id; 59 t[cur].l = t[u].l; 60 t[cur].r = t[u].r; 61 t[cur].w = t[u].w + 1; 62 if (l < r) 63 { 64 int mid = (l + r) >> 1; 65 if (k <= mid) t[cur].l = Add(t[u].l, l, mid, k); 66 else t[cur].r = Add(t[u].r, mid + 1, r, k); 67 } 68 return cur; 69 } 70 71 int Query(int u, int v, int l, int r, int k) 72 { 73 if (l == r) return l; 74 int df = t[t[v].l].w - t[t[u].l].w; 75 int mid = (l + r) >> 1; 76 if (df < k) return Query(t[u].r, t[v].r, mid + 1, r, k - df); 77 else return Query(t[u].l, t[v].l, l, mid, k); 78 } 79 80 signed main() 81 { 82 read(n), read(m); 83 for (int i = 1; i <= n; ++i) read(a[i]), b[i] = a[i]; 84 std::sort(a + 1, a + n + 1); 85 cnt = std::unique(a + 1, a + n + 1) - a - 1; 86 Build(root[0] = ++id, 1, cnt); 87 for (int i = 1; i <= n; ++i) 88 root[i] = Add(root[i - 1], 1, cnt, Lsh(b[i])); 89 for (int i = 1; i <= m; ++i) 90 { 91 read(L), read(R), read(K); 92 int p = Query(root[L - 1], root[R], 1, cnt, K); 93 printf("%d ", a[p]); 94 } 95 return 0; 96 }