NC16564 借教室

二分检验+差分

#include <iostream>
using namespace std;
const int maxn = 1000010;
int n, m;
long long arr[maxn];//每天借多少个教室
long long arr2[maxn];//教室差分
struct Node {
    long long num;
    int beginDay;
    int endDay;
}dingdan[maxn];

bool judge(int num) {
    for (int i = 0; i < maxn; i++) {
        arr2[i] = 0;
    }
    int sum = 0;
    for (int i = 1; i <= num; i++) {
        arr2[dingdan[i].beginDay] += dingdan[i].num;
        arr2[dingdan[i].endDay + 1] -= dingdan[i].num;
    }
    for (int i = 1; i <= n; i++) {
        sum += arr2[i];
        if (sum > arr[i])return false;
    }
    return true;
}
int find(int l, int r) {
    while (l < r) {
        int mid = (r - l) / 2 + l;
        if (judge(mid))l = mid + 1;
        else r = mid;
    }
    return l;
}
int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> arr[i];
    }
    for (int i = 1; i <= m; i++) {
        cin >> dingdan[i].num >> dingdan[i].beginDay >> dingdan[i].endDay;
    }
    if (find(1, m) < m) {
        cout << "-1" << endl << find(1, m);
    }
    else {
        cout << "0";
    }

}