【每日一题】 换个角度思考
换个角度思考
https://ac.nowcoder.com/acm/problem/19427
solution
发现可以离线。
将所有询问离线下来,按照查询的从小到大排序。并且将数组
从小到大排序。按照
从小到大的枚举每次询问,同时将所有
的数字,将树状数组上
位置
。然后直接区间查询就行了。
code
/*
* @Author: wxyww
* @Date: 2020-04-29 11:36:43
* @Last Modified time: 2020-04-29 11:41:07
*/
#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<queue>
#include<vector>
#include<ctime>
#include<cmath>
using namespace std;
typedef long long ll;
const int N = 100010;
ll read() {
ll x = 0,f = 1;char c = getchar();
while(c < '0' || c > '9') {
if(c == '-') f = -1; c = getchar();
}
while(c >= '0' && c <= '9') {
x = x * 10 + c - '0'; c = getchar();
}
return x * f;
}
#define pi pair<int,int>
pi a[N];
struct node {
int l,r,x,id;
}Q[N];
bool cmp(const node &A,const node &B) {
return A.x < B.x;
}
int ans[N],tree[N],n;
void update(int pos,int c) {
while(pos <= n) {
tree[pos] += c;
pos += pos & -pos;
}
}
int query(int pos) {
int ret = 0;
while(pos) {
ret += tree[pos];
pos -= pos & -pos;
}
return ret;
}
int main() {
n = read();int m = read();
for(int i = 1;i <= n;++i) a[i].first = read(),a[i].second = i;
sort(a + 1,a + n + 1);
for(int i = 1;i <= m;++i) {
Q[i].l = read(),Q[i].r = read();Q[i].x = read();
Q[i].id = i;
}
sort(Q + 1,Q + m + 1,cmp);
int p = 1;
for(int i = 1;i <= m;++i) {
while(a[p].first <= Q[i].x && p <= n) {
update(a[p].second,1);
++p;
}
ans[Q[i].id] = query(Q[i].r) - query(Q[i].l - 1);
}
for(int i = 1;i <= m;++i) printf("%d\n",ans[i]);
return 0;
}
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