Determine if Two Events Have Conflict - Practice Coding Problems

Determine if Two Events Have Conflict - Problem

Array String Easy

You are given two arrays of strings that represent two inclusive events that happened on the same day, event1 and event2, where:

event1 = [startTime1, endTime1] and event2 = [startTime2, endTime2].

Event times are valid 24 hours format in the form of HH:MM.

A conflict happens when two events have some non-empty intersection (i.e., some moment is common to both events).

Return true if there is a conflict between two events. Otherwise, return false.

Input & Output

Example 1 — Basic Overlap

$ Input: event1 = ["01:15", "02:00"], event2 = ["01:30", "03:00"]

› Output: true

💡 Note: Events overlap from 01:30 to 02:00. Since event1 starts at 01:15 (before event2 ends at 03:00) and event2 starts at 01:30 (before event1 ends at 02:00), there is a conflict.

Example 2 — No Overlap

$ Input: event1 = ["01:00", "02:00"], event2 = ["03:00", "04:00"]

› Output: false

💡 Note: Events do not overlap. Event1 ends at 02:00 before event2 starts at 03:00, so there is no time conflict.

Example 3 — Edge Touch

$ Input: event1 = ["10:00", "11:00"], event2 = ["11:00", "12:00"]

› Output: true

💡 Note: Events touch at exactly 11:00. Since the problem states events are inclusive, they share the moment 11:00, which counts as a conflict.

Constraints

event1.length == event2.length == 2
event1[i] and event2[i] are in HH:MM format
All event times are valid 24-hour format

Visualization

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Understanding the Visualization

Input Events

Two events with start and end times in HH:MM format

Overlap Check

Compare if event1 starts before event2 ends AND event2 starts before event1 ends

Conflict Result

Return true if both conditions are met (overlap exists)

Key Takeaway

🎯 Key Insight: Two intervals overlap if each starts before the other ends

Asked in

a Amazon 15 G Google 12 M Microsoft 8

The key insight is that two time intervals overlap if each interval starts before the other ends. The optimal approach uses direct string comparison since HH:MM format is lexicographically comparable. Time: O(1), Space: O(1)

Common Approaches

Approach	Time	Space	Notes
✓ String Comparison	O(1)	O(1)	Compare time strings directly using lexicographic ordering
Time Conversion to Minutes	O(1)	O(1)	Convert time strings to minutes since midnight for numeric comparison

String Comparison — Algorithm Steps

Step 1: Compare if event1 starts before event2 ends
Step 2: Compare if event2 starts before event1 ends
Step 3: Return true if both conditions are met

Visualization

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Step-by-Step Walkthrough

Compare Start Times

Check if event1 starts before event2 ends

Compare End Times

Check if event2 starts before event1 ends

Overlap Result

Both conditions true means overlap exists

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int solution(char event1[][6], char event2[][6]) {
    // Two events overlap if:
    // event1 starts before or when event2 ends AND
    // event2 starts before or when event1 ends
    return strcmp(event1[0], event2[1]) <= 0 && strcmp(event2[0], event1[1]) <= 0;
}

int main() {
    char line[100];
    char event1[2][6], event2[2][6];
    
    // Parse first event
    fgets(line, sizeof(line), stdin);
    sscanf(line, "[\"%[^\"]\",\"%[^\"]\"]", event1[0], event1[1]);
    
    // Parse second event
    fgets(line, sizeof(line), stdin);
    sscanf(line, "[\"%[^\"]\",\"%[^\"]\"]", event2[0], event2[1]);
    
    int result = solution(event1, event2);
    printf(result ? "true\n" : "false\n");
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

String comparison of fixed-length strings (5 chars) is constant time

✓ Linear Growth

Space Complexity

O(1)

Only using a few variables for comparison

✓ Linear Space

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

String Comparison — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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