Rosetta Code Challenges - LU decomposition

Rosetta Code
1

Tell us what’s happening:

I tried to complete the project and I got this error message and no response to this request // running tests
4. luDecomposition([[11, 9, 24, 2], [1, 5, 2, 6], [3, 17, 18, 1], [2, 5, 7, 1]]) should return [[[1, 0, 0, 0], [0.2727272727272727, 1, 0, 0], [0.09090909090909091, 0.2875, 1, 0], [0.18181818181818182, 0.23124999999999996, 0.0035971223021580693, 1]], [[11, 9, 24, 2], [0, 14.545454545454547, 11.454545454545455, 0.4545454545454546], [0, 0, -3.4749999999999996, 5.6875], [0, 0, 0, 0.510791366

Your code so far

function luDecomposition(A) {
    const n = A.length;
    const L = Array.from({ length: n }, () => Array(n).fill(0));
    const U = Array.from({ length: n }, () => Array(n).fill(0));
    const P = Array.from({ length: n }, () => Array(n).fill(0));

    // Initialize the permutation matrix
    for (let i = 0; i < n; i++) {
        P[i][i] = 1;
    }

    for (let i = 0; i < n; i++) {
        // Pivoting
        let maxIndex = i;
        for (let j = i + 1; j < n; j++) {
            if (Math.abs(A[j][i]) > Math.abs(A[maxIndex][i])) {
                maxIndex = j;
            }
        }
        if (i !== maxIndex) {
            [A[i], A[maxIndex]] = [A[maxIndex], A[i]];
            [P[i], P[maxIndex]] = [P[maxIndex], P[i]];
            [L[i], L[maxIndex]] = [L[maxIndex], L[i]]; // Swap rows of L to maintain consistency
        }

        // Decomposition
        for (let j = i; j < n; j++) {
            let sum = 0;
            for (let k = 0; k < i; k++) {
                sum += L[i][k] * U[k][j];
            }
            U[i][j] = A[i][j] - sum;
        }

        for (let j = i + 1; j < n; j++) {
            let sum = 0;
            for (let k = 0; k < i; k++) {
                sum += L[j][k] * U[k][i];
            }
            L[j][i] = (A[j][i] - sum) / U[i][i];
        }
        L[i][i] = 1;
    }

    return [L, U, P];
}

// Example Tests:
const result1 = luDecomposition([[1, 3, 5], [2, 4, 7], [1, 1, 0]]);
console.log('L:', result1[0]);
console.log('U:', result1[1]);
console.log('P:', result1[2]);

const result2 = luDecomposition([[11, 9, 24, 2], [1, 5, 2, 6], [3, 17, 18, 1], [2, 5, 7, 1]]);
console.log('L:', result2[0]);
console.log('U:', result2[1]);
console.log('P:', result2[2]);

const result3 = luDecomposition([[1, 1, 1], [4, 3, -1], [3, 5, 3]]);
console.log('L:', result3[0]);
console.log('U:', result3[1]);
console.log('P:', result3[2]);

const result4 = luDecomposition([[1, -2, 3], [2, -5, 12], [0, 2, -10]]);
console.log('L:', result4[0]);
console.log('U:', result4[1]);
console.log('P:', result4[2]);

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Challenge Information:

Rosetta Code Challenges - LU decomposition

2

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