[CF1042D] Petya and Array

题面

题解

这道题目到底叫什么好呢？？

史上最短CDQ分治题

记一个前缀和，然后CDQ分治即可。

代码

#include<cstdio>
#include<algorithm>
#define RG register

inline long long read()
{
	long long data = 0, w = 1;
	char ch = getchar();
	while(ch != '-' && (ch < '0' || ch > '9')) ch = getchar();
	if(ch == '-') w = -1, ch = getchar();
	while(ch >= '0' && ch <= '9') data = data * 10 + (ch ^ 48), ch = getchar();
	return data*w;
}

const int maxn(2e5 + 10);
int n;
long long sum[maxn], t, ans;

void Div(long long *beg, long long *end)
{
	if(end - beg <= 1) return;
	long long *mid = beg + ((end - beg) >> 1);
	Div(beg, mid); Div(mid, end);

	for(long long *i = beg, *j = mid; i != mid; ++i, ans += j - mid)
		while(j != end && (*j) < t + (*i)) ++j;
	std::inplace_merge(beg, mid, end);
}

int main()
{
	n = read(); t = read();
	for(RG int i = 1; i <= n; i++) sum[i] = sum[i - 1] + read();
	Div(sum, sum + n + 1); printf("%lld\n", ans);
	return 0;
}