JavaScript Program to find Maximum Distance Between two Occurrences of Same Element in Array

function maxDistance(arr) {
    let dict = {};
    let maxD = -1;

    for (let i = 0; i < arr.length; i++) {
        if (dict[arr[i]] !== undefined) {
            maxD = Math.max(maxD, i - dict[arr[i]]);
        } else {
            dict[arr[i]] = i;
        }
    }

    return maxD;
}

let arr = [1, 2, 4, 1, 3, 4, 2, 5, 6, 5];
console.log(
    "Max distance between occurrences of same element: " 
        + maxDistance(arr));

function maxDistance(arr, n) {
    let map = new Map();
    let maxDist = 0;

    for (let i = 0; i < n; i++) {
        if (!map.has(arr[i]))
            map.set(arr[i], i);
        else
            maxDist = Math.max(maxDist, i - map.get(arr[i]));
    }

    return maxDist;
}


let arr = [1, 2, 4, 1, 3, 4, 2, 5, 6, 5];
console.log(
    "Max distance between occurrences of same element: " 
        + maxDistance(arr,10));

function maxDistance(arr) {
    const elementIndices = {};

    // Store indices of each element
    for (let i = 0; i < arr.length; i++) {
        if (elementIndices[arr[i]] === undefined) {
            elementIndices[arr[i]] = [];
        }
        elementIndices[arr[i]].push(i);
    }

    let maxDist = -1;

    // Iterate through each element in the dictionary
    for (const key in elementIndices) {
        const indices = elementIndices[key];
        if (indices.length > 1) {
            // Find the max distance using first and last index
            const dist = indices[indices.length - 1] - indices[0];
            maxDist = Math.max(maxDist, dist);
        }
    }

    return maxDist;
}

// Examples
const arr1 = [3, 2, 1, 2, 1, 4, 5, 8, 6, 7, 4, 2];
console.log(maxDistance(arr1)); // Output: 10

const arr2 = [1, 1, 1, 1];
console.log(maxDistance(arr2)); // Output: 3

const arr3 = [1, 2, 3, 4, 5];
console.log(maxDistance(arr3)); // Output: -1 (no repeated elements)

function maxDistance(arr) {
    let map = new Map();
    let maxDist = -1; 

    for (let i = 0; i < arr.length; i++) {
        if (!map.has(arr[i])) {
            map.set(arr[i], i);
        } else {
            const firstIndex = map.get(arr[i]);
            maxDist = Math.max(maxDist, i - firstIndex);
        }
    }

    return maxDist;
}
const arr1 = [3, 2, 1, 2, 1, 4, 5, 8, 6, 7, 4, 2];
console.log(maxDistance(arr1));

const arr2 = [1, 1, 1, 1];
console.log(maxDistance(arr2)); 

const arr3 = [1, 2, 3, 4, 5];
console.log(maxDistance(arr3));