二分申请人编号 O(nlogm) check函数内做差分
因为输出时为l + 1 因此l的左端点应为0.
差分数组需要备份 每次二分需要复用

代码:
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e6 + 10;
int n, m;
ll a[N], b[N], d[N], s[N], t[N], back[N];
bool flag = 1;

bool check(int x)
{
    memcpy(b, back, sizeof back);
    for(int i = 1;i <= x;i++)
    {
        b[s[i]] -= d[i];
        b[t[i] + 1] += d[i];
    }

    for(int i = 1;i <= n;i++)
    {
    b[i] += b[i - 1];
    if(b[i] < 0)
    {
        flag = 0;
        return false;
    }
    }
    return true;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> n >> m;
    for(int i = 1;i <= n;i++)
    {
        cin >> a[i];
        b[i] = a[i] - a[i - 1];
    }
    memcpy(back, b, sizeof b);

    for(int i = 1;i <= m;i++)
    {
        cin >> d[i] >> s[i] >> t[i];
    }

    int l = 0, r = m;
    while(l < r)
    {
        int mid = (l + r + 1) >> 1;
        if(check(mid))l = mid;
        else r = mid - 1;
    }
    if(!flag)cout << "-1\n" << l + 1;
    else cout << 0;
    return 0;
}