P1083 借教室

思路：前缀和， c表示对于当前的middle， 前缀和

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6+1;
int n, m, now, r[maxn], d[maxn], s[maxn], t[maxn], c[maxn];
bool check(int x) {
	int i, sum = 0;
	if(now > x) {
		for(i = x + 1; i <= now; i++) {
			c[s[i]] -= d[i];
			c[t[i] + 1] += d[i];
		}
	}
	else {
		for(i = now + 1; i <= x; i++) {
			c[s[i]] += d[i];
			c[t[i] + 1] -= d[i];
		}
	}
	now = x;
	for(int i = 1; i <= n; i++) {
		sum += c[i];
		if(sum > r[i]) return true;
	}
	return false;
}
int main() {
	cin >> n >> m;
	for(int i = 1; i <= n; i++) {
		cin >> r[i];
	}
	for(int i = 1; i <= m; i++) cin >> d[i] >> s[i] >> t[i];
	int left = 1, right = m, ans = 0x3f3f3f;
	while(left <= right) {
		int middle = (left + right) / 2;
		if(check(middle)) ans = min(ans, middle), right = middle - 1;
		else left = middle + 1;
	}
	if(ans == 0x3f3f3f) cout << 0;
	else cout << -1 << endl << ans;
	return 0;
}