差分数组维护每个位置被修改的次数。

#include <bits/stdc++.h>
#define int long long
using namespace std;
int n, m;
int a[100000 + 5];
int f[100000 + 5]; 
signed main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    for (int i = 1; i <= m; i++)
    {
        int l, r;
        cin >> l >> r;
        f[l]++;
        f[r + 1]--;
    }
    int now = 0;
    int ans = 0;
    for (int i = 1; i <= n; i++)
    {
        now += f[i];
        if (now > 0 && a[i] % 2 == 1)
            a[i]++;
        ans += a[i];
    }
    cout << ans;
    return 0;
}