ADVANCED DATA STRUCTURES PROGRAM • LEVEL 17 — ADVANCED HEAPS

Merge K Sorted Linked Lists with a Heap

Learn how to merge k sorted linked lists with a heap using a clear C program.

AdvancedHeap variantsPriority queue

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

1 2 3 4 5 6 7 8 9

COMPLETE C PROGRAM

Complete C implementation

#include <stdio.h>
#include <stddef.h>

struct Node { int value; struct Node *next; };

int main(void)
{
    struct Node a3={7,NULL},a2={4,&a3},a1={1,&a2},b3={8,NULL},b2={5,&b3},b1={2,&b2},c3={9,NULL},c2={6,&c3},c1={3,&c2};
    struct Node *heads[] = {&a1,&b1,&c1};
    for (int out = 0; out < 9; out++) { int best = -1; for (int i = 0; i < 3; i++) if (heads[i] && (best < 0 || heads[i]->value < heads[best]->value)) best = i; printf("%d%c", heads[best]->value, out == 8 ? '\n' : ' '); heads[best] = heads[best]->next; }
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

1 2 3 4 5 6 7 8 9

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Keep one candidate from each list and repeatedly advance the list containing the smallest head.
Display the computed result.

Keep one candidate from each list and repeatedly advance the list containing the smallest head.

EFFICIENCY

Time and space complexity

Time complexity

O(total * k) demonstration

Auxiliary space

O(k)

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.