C Exercises: Find largest number possible from the set of specified numbers

Last update on March 18 2025 13:21:05 (UTC/GMT +8 hours)

76. Largest Number from Given Set

Write a program in C to find the largest number possible from the set of given numbers.

Expected Output:
The given numbers are :
15 628 971 9 2143 12
The largest possible number by the given numbers are: 997162821431512

The problem involves writing a C program that arranges a set of given numbers to form the largest possible number. The program should take the individual numbers, determine the optimal order to concatenate them for the largest numerical value, and then display the resulting number. This requires comparing and sorting the numbers based on their potential contribution to the final combined value.

Visual Presentation:

Sample Solution:

C Code:

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

// Comparison function for qsort to sort strings in a specific order to form the largest number
int compare(const void *a, const void *b) {
    const char **X = (const char **)a;
    const char **Y = (const char **)b;

    // Determine the combined lengths of strings a and b, plus 1 for null terminator
    int chr_len = strlen(*X) + strlen(*Y) + 1;

    // Concatenate strings a and b in one order
    char XY[chr_len];
    strcpy(XY, *X);
    strcat(XY, *Y);

    // Concatenate strings b and a in another order
    char YX[chr_len];
    strcpy(YX, *Y);
    strcat(YX, *X);

    // Compare the concatenated strings to sort in descending order
    return strcmp(YX, XY);
}

int main(void) {
    // Array of strings
    char *arr1[] = { "15", "628", "971", "9", "2143", "12" };
    int n = sizeof(arr1) / sizeof(arr1[0]);
    int i;

    // Print original array
    printf("The given numbers are :  \n");
    for (i = 0; i < n; i++) {
        printf("%s  ", arr1[i]);
    }
    printf("\n");

    // Sort the array using qsort with custom comparison function
    qsort(arr1, n, sizeof(arr1[0]), compare);

    // Print the largest possible number formed by the given numbers
    printf("The largest possible number by the given numbers are: ");
    for (int i = 0; i < n; i++) {
        printf("%s", arr1[i]);
    }
    return 0;
}

Output:

The given numbers are :  
15  628  971  9  2143  12  
The largest possible number by the given numbers are: 997162821431512

Flowchart:/p>

For more Practice: Solve these Related Problems:

• Write a C program to form the largest possible number by concatenating an array of numbers using a custom comparator.
• Write a C program to arrange numbers to form the maximum possible numerical value without converting them to strings.
• Write a C program to generate all possible concatenations of numbers from an array and then choose the largest.
• Write a C program to rearrange numbers in an array using sorting by comparing string representations and then output the result.

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