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How can I find the L.C.M of a series of numbers

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  • Latest Post Latest Post by ajay.krish123

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For : the usual, reliable method is to fold pairwise LCMs using the Euclidean gcd. Use the identity

lcm(a,b) = abs((a / gcd(a,b)) * b)

and apply it iteratively across the list: l = lcm(l, next). This avoids brute-force searching and is fast. Background on the definition is available at Least common multiple. As suggested, sketching pseudocode first helps surface edge cases.

A compact C-style implementation (illustrative; checks for overflow via GCC/Clang __int128):

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

long long gcd(long long a, long long b) {
    if (a < 0) a = -a;
    if (b < 0) b = -b;
    while (b) {
        long long t = a % b;
        a = b;
        b = t;
    }
    return a;
}

long long lcm(long long a, long long b) {
    if (a == 0 || b == 0) return 0;
    long long g = gcd(a, b);
    __int128 prod = (__int128)(a / g) * (__int128)b;
    if (prod > LLONG_MAX || prod < LLONG_MIN) {
        fprintf(stderr, "overflow computing lcm\n");
        exit(1);
    }
    long long r = (long long)prod;
    return r < 0 ? -r : r;
}

long long lcm_array(const long long *arr, size_t n) {
    if (n == 0) return 1; /* convention; otherwise undefined */
    long long res = arr[0];
    for (size_t i = 1; i < n; ++i) res = lcm(res, arr[i]);
    return res;
}

Notes and cautions: lcm(0,x) is 0 for x != 0; gcd(0,0) is 0 so avoid dividing by zero. Use absolute values for negatives. Multiplication can overflow—use __int128, a big-integer library, or drop to a language with built-in big integers for very large inputs. Time complexity is dominated by gcd computations (roughly O(n log M)). This gives a direct programming answer (the clarification asked by ) while following ’s advice to think in pseudocode first; general tutorials like those mentioned by exist, but the code above is a practical, precise implementation ready to adapt.

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Member Avatar for William Hemsworth

Why dont you ask google that, and we will help with any specific problems you have.

Member Avatar for MosaicFuneral

Finish pre-Algebra.

Member Avatar for ajay.krish123

Is it the programming question or mathematical question??

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