hdoj 4417

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题目：

hdoj ： http://acm.hdu.edu.cn/showproblem.php?pid=4417

思路：

将砖块与问题都按高度排序，并用变量标记其位置，之后利用树状数组的特点，在每个问题询问前将这个高度前的砖块更新入树状数组中，之后查询并将结果记录在ans数组中即可。

AC代码：

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;#define lowbit(x) x & (-x)const int M = 100000 + 10;struct Height{int l, r, h, dx;bool operator <(const Height &i)const{return h < i.h;}}q[M], h[M];int ans[M], n, tree[M];void add(int a){while(a <= n){tree[a]++;a += lowbit(a);}}int sum(int a){int res = 0;while(a > 0){res += tree[a];a -= lowbit(a);}return res;}main(){int T;scanf("%d", &T);for(int p = 1; p <= T; p++){memset(tree, 0, sizeof(tree));int qs;scanf("%d %d", &n, &qs);for(int i = 1; i <= n; i++){scanf("%d", &h[i].h);h[i].dx = i;}for(int i = 1; i <= qs; i++){scanf("%d %d %d", &q[i].l, &q[i].r, &q[i].h);q[i].l++;q[i].r++;q[i].dx = i;}sort(h + 1, h + 1 + n);sort(q + 1, q + qs + 1);for(int i = 1, j = 1; i <= qs; i++)//i = query j = nums{while(j <= n && h[j].h <= q[i].h)//更新砖块高度至询问高度{add(h[j].dx);j++;}ans[q[i].dx] = sum(q[i].r) - sum(q[i].l - 1);}printf("Case %d:\n", p);for(int i = 1; i <= qs; i++)printf("%d\n", ans[i]);}}

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