Determine if Two Events Have Conflict

easy intervals overlap string parsing

Problem

You are given two inclusive events on the same day as event1 = [start1, end1] and event2 = [start2, end2], where each time is a valid 24-hour string HH:MM. A conflict happens when the two events share at least one common moment. Return true if they conflict, otherwise false.

Inputevent1 = ["01:00","02:00"], event2 = ["01:20","03:00"]

Outputtrue

The events intersect from 01:20 to 02:00.

Inputevent1 = ["10:00","11:00"], event2 = ["14:00","15:00"]

Outputfalse

Event 1 ends at 11:00, long before event 2 starts at 14:00 — no shared moment.

event1 (start, end as HH:MM)

event2 (start, end as HH:MM)

def have_conflict(event1, event2):
    def to_min(t):
        h, m = t.split(":")
        return int(h) * 60 + int(m)
    s1, e1 = to_min(event1[0]), to_min(event1[1])
    s2, e2 = to_min(event2[0]), to_min(event2[1])
    return s1 <= e2 and s2 <= e1

function haveConflict(event1, event2) {
  const toMin = (t) => {
    const [h, m] = t.split(":");
    return Number(h) * 60 + Number(m);
  };
  const s1 = toMin(event1[0]), e1 = toMin(event1[1]);
  const s2 = toMin(event2[0]), e2 = toMin(event2[1]);
  return s1 <= e2 && s2 <= e1;
}

boolean haveConflict(String[] event1, String[] event2) {
    int s1 = toMin(event1[0]), e1 = toMin(event1[1]);
    int s2 = toMin(event2[0]), e2 = toMin(event2[1]);
    return s1 <= e2 && s2 <= e1;
}

int toMin(String t) {
    String[] p = t.split(":");
    return Integer.parseInt(p[0]) * 60 + Integer.parseInt(p[1]);
}

int toMin(string t) {
    return stoi(t.substr(0, 2)) * 60 + stoi(t.substr(3, 2));
}

bool haveConflict(vector<string>& event1, vector<string>& event2) {
    int s1 = toMin(event1[0]), e1 = toMin(event1[1]);
    int s2 = toMin(event2[0]), e2 = toMin(event2[1]);
    return s1 <= e2 && s2 <= e1;
}

Explanation

Each event is an inclusive interval on the timeline of a single day. The first job is to make the two events comparable: parse each HH:MM string into a single integer — its minute offset from midnight — with to_min(t) = 60·HH + MM. After that, every time is just a number from 0 to 1439.

Now the question "do the events share a moment?" becomes the classic interval overlap test. Two intervals [s1, e1] and [s2, e2] overlap exactly when each one starts no later than the other one ends: s1 ≤ e2 and s2 ≤ e1.

It is easier to see why by negating it. The events fail to overlap only when one finishes strictly before the other begins — that is, e1 < s2 (event 1 entirely to the left) or e2 < s1 (event 2 entirely to the left). The complement of those two disjoint cases is precisely s1 ≤ e2 and s2 ≤ e1.

Because the events are inclusive, touching endpoints count as a conflict: ["01:15","02:00"] and ["02:00","03:00"] share the single instant 02:00, so the ≤ (not <) is exactly right.

The whole solution is constant work: two string splits, a handful of integer operations, and one boolean — no loops, no sorting.

Time: O(1) Space: O(1)