Sum of Intervals

• Time : $O(nlogn)$
• Space : $O(1)$

#include <vector>
#include <utility>
using namespace std;
int sum_intervals(std::vector<std::pair<int, int>> A) {
    sort(begin(A), end(A));
    long long res = 0, le = -2147483648ll, ri = -2147483648ll;
    for(auto [l,r] : A) {
        if(l < ri) ri = max(ri, r * 1ll);
        else {
            res += ri - le;
            le = l, ri = r;
        }
    }
    res += ri - le;
    return res;
}