DATA STRUCTURES PROGRAM • ARRAY TECHNIQUES

Apply Range Updates with a Difference Array

Learn how to apply range updates with a difference array using a clear C program.

IntermediateDifference arrayRange updatePrefix reconstruction

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

10 15 15 15 10

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>

int main(void)
{
    int values[] = {10, 10, 10, 10, 10};
    int difference[6] = {values[0], 0, 0, 0, 0, 0};
    for (int index = 1; index < 5; index++) difference[index] = values[index] - values[index - 1];
    int left = 1, right = 3, amount = 5;
    difference[left] += amount;
    difference[right + 1] -= amount;
    int current = 0;
    for (int index = 0; index < 5; index++) {
        current += difference[index];
        printf("%d ", current);
    }
    putchar('\n');
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

10 15 15 15 10

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Mark only the update boundaries, then recover final values with a prefix sum.
Display the computed result.

Mark only the update boundaries, then recover final values with a prefix sum.

EFFICIENCY

Time and space complexity

Time complexity

O(1) update, O(n) reconstruction

Auxiliary space

O(n)

DEBUGGING CHECKLIST

Common mistakes

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Use the correct format specifier for every variable.

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Initialize variables before using their values.

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Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.