[noip2012]借教室

可以线段树或者二分。

线段树会被卡，二分写不好也会被卡。

所以用二分。

读入用getchar()的话可以减少一半以上的时间。

#include <cstdio>
const int N = 1000000 + 9;
long long delta[N];
int idx[N],a[N],n,m,d[N],s[N],t[N],pre;
inline bool check(const int mid)
{
	long long sum = 0;
	if (pre < mid)
		for (int i = pre + 1; i <= mid; ++i)
			delta[s[i]] += d[i],delta[t[i] + 1] -= d[i];
	else 
		for (int i = mid + 1; i <= pre; ++i)
			delta[s[i]] -= d[i],delta[t[i] + 1] += d[i];
	pre = mid;
	for (int i = 1; i <= n; ++i)
		if ((sum += delta[i]) > a[i]) return false;
	return true;
}
inline void read(int &x)
{
	char c;
	while ((c = getchar()) < '0');
	while (c >= '0') {
		x = x * 10 + c - '0';
		c = getchar();
	}
}
int main()
{
	#ifndef ONLINE_JUDGE
	freopen("classroom.in","r",stdin);
	freopen("classroom.out","w",stdout);
	#endif
	read(n);read(m);
	for (int i = 1; i <= n; ++i) read(a[i]);
	for (int i = 1; i <= m; ++i) {
		read(d[i]);read(s[i]);read(t[i]);
	}
	int l = 0,r = n + 1;
	while (l + 1 < r) {
		const int mid = (l + r)/2; 
		if (check(mid)) l = mid;
		else r = mid;
	}
	if (l == n) puts("0");
	else printf("-1\n%d\n",r);
}