POJ2104 K-th Number(线段树)

题目链接 K-th Number

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>

 using namespace std;

 #define rep(i, a, b)    for (int i(a); i <= (b); ++i)
 #define lson        i << 1, L, mid
 #define rson        i << 1 | 1, mid + 1, R

 const int N = ;

 struct node{
     int l, r;
 } tree[N << ];

 int a[N], b[N], d[N * ];
 int cnt = ;
 int n, q;

 void build(int i, int L, int R){
     if (L == R){
         d[++cnt] = a[L];
         tree[i].l = cnt;
         tree[i].r = cnt;
         return;
     }

     int mid = (L + R) >> ;
     build(lson);
     build(rson);
     tree[i].l = cnt + ;
     int l1 = tree[i << ].l, r1 = tree[i << ].r;
     int l2 = tree[i <<  | ].l, r2 = tree[i <<  | ].r;

     while (l1 <= r1 && l2 <= r2){
         if (d[l1] < d[l2]) d[++cnt] = d[l1++];
         else d[++cnt] = d[l2++];
     }

     while (l1 <= r1) d[++cnt] = d[l1++];
     while (l2 <= r2) d[++cnt] = d[l2++];
     tree[i].r = cnt;
 }

 int binary(int l, int r, int tmp){
     if (tmp >= d[r]) return r - l + ;
     if (tmp < d[l]) return ;
     int L = l, R = r;
     while (L < R){
         int mid = (L + R) >> ;
         if (d[mid] > tmp) R = mid; else L = mid + ;
     }

     return L - l;
 }

 int query(int i, int L, int R, int l, int r, int tmp){
     if (l <= L && R <= r) return binary(tree[i].l, tree[i].r, tmp);
     int mid = (L + R) >> , ret = ;
     if (l <= mid) ret += query(lson, l, r, tmp);
     if (r > mid) ret += query(rson, l, r, tmp);
     return ret;
 }

 int main(){

     scanf("%d%d", &n, &q);
     rep(i, , n) scanf("%d", a + i);
     build(, , n);
     rep(i, , n) b[i] = a[i];
     sort(b + , b + n + );

     rep(i, , q){
         int l, r, tmp;
         scanf("%d%d%d", &l, &r, &tmp);
         int s = , t = n;
         while (s < t){
             int mid = (s + t) >> ;
             int t1 = query(, , n, l, r, b[mid]);
             if (t1 < tmp) s = mid + ;
             else t = mid;
         }

         printf("%d\n", b[s]);
     }

     return ;
 }