2020牛客多校二 G. Greater and Greater (双指针+bitset优化)

题意：给定长度为n的序列a，和长度为m的序列b，问有序列a中有多少个长度为m的连续子区间s，满足s(i)>=b(i)。

题解：双指针+bitset优化

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#include<queue>
#include<stack>
#include<cmath>
#include<vector>
#include<fstream>
#include<set>
#include<map>
#include<sstream>
#include<iomanip>
#include<bitset>
#define ll long long
using namespace std;
int n, m, x;
vector<pair<int, int> > a, b;
bitset<150005> res, ans;
int main() {
	scanf("%d%d", &n, &m);
	for (int i = 0; i < n; i++) scanf("%d", &x), a.push_back(make_pair(x, i));
	for (int i = 0; i < m; i++) scanf("%d", &x), b.push_back(make_pair(x, i));
	sort(a.begin(), a.end());
	sort(b.begin(), b.end());
	ans.set();
	for (int i = m - 1, j = n - 1; i >= 0; i--) {
		while (j >= 0 && a[j].first >= b[i].first) {
			res.set(a[j--].second);
		}
		ans &= (res >> b[i].second);
	}
	printf("%d\n", ans.count());
	return 0;
}