Debounce

Debounce - Problem

JavaScript Medium

Given a function fn and a time in milliseconds t, return a debounced version of that function.

A debounced function is a function whose execution is delayed by t milliseconds and whose execution is cancelled if it is called again within that window of time. The debounced function should also receive the passed parameters.

Example: If t = 50ms, and the function was called at 30ms, 60ms, and 100ms:

The first 2 function calls would be cancelled
The 3rd function call would be executed at 150ms

If instead t = 35ms:

The 1st call would be cancelled
The 2nd would be executed at 95ms
The 3rd would be executed at 135ms

Note: You cannot use lodash's _.debounce() function.

Input & Output

Example 1 — Basic Debouncing

$ Input: t = 50, calls at [30ms, 60ms, 100ms]

› Output: Function executes once at 150ms

💡 Note: First two calls are cancelled by subsequent calls. The third call executes after 50ms delay (at 150ms total).

Example 2 — Shorter Delay

$ Input: t = 35, calls at [30ms, 60ms, 100ms]

› Output: Function executes at 95ms and 135ms

💡 Note: First call cancelled. Second call executes at 95ms (60+35). Third call executes at 135ms (100+35).

Example 3 — Single Call

$ Input: t = 100, single call at 50ms

› Output: Function executes at 150ms

💡 Note: With no subsequent calls to cancel it, the function executes after the full delay.

Constraints

0 ≤ t ≤ 1000
fn is a valid function
At most 10 function calls will be made

Visualization

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Asked in

G Google 35 f Facebook 28 a Amazon 22 N Netflix 18

The key insight is to use a closure that maintains a timer reference, cancelling the previous timer each time the function is called and setting a new one. The timer-based approach correctly implements debouncing with Time: O(1), Space: O(1).

Common Approaches

Approach	Time	Space	Notes
✓ Timer-Based Debouncing	O(1)	O(1)	Use setTimeout to delay execution and clearTimeout to cancel previous calls
Immediate Execution	O(1)	O(1)	Execute function immediately without debouncing

Timer-Based Debouncing — Algorithm Steps

Step 1: Clear any existing timer
Step 2: Set new timer with delay t
Step 3: Execute function only when timer completes

Visualization

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Step-by-Step Walkthrough

Setup Timer

Each call sets a timer for t milliseconds

Cancel & Reset

New calls cancel previous timer and set new one

Execute Last

Only the final call executes after delay

Code -

solution.c — C

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

typedef struct {
    void (*fn)(int*, int);
    int* args;
    int argCount;
    int delay;
    int cancelled;
} DebounceData;

void* timerThread(void* arg) {
    DebounceData* data = (DebounceData*)arg;
    usleep(data->delay * 1000); // Convert ms to microseconds
    
    if (!data->cancelled) {
        data->fn(data->args, data->argCount);
    }
    
    free(data->args);
    free(data);
    return NULL;
}

void testFunction(int* args, int len) {
    printf("Executed\n");
}

int main() {
    char fnCode[1000];
    fgets(fnCode, sizeof(fnCode), stdin);
    int t;
    scanf("%d", &t);
    
    printf("function\n");
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Each function call only performs timer operations which are O(1)

✓ Linear Growth

Space Complexity

O(1)

Only stores one timer reference regardless of number of calls

✓ Linear Space

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Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Timer-Based Debouncing — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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