/**
 * @param {number[]} nums
 * @return {number}
 */
var findUnsortedSubarray = function(nums) {
    if (nums.length < 2 || !nums) return 0;
    
    // find largest index out of place
    let end = 0;
    let leftPointer = nums[end];
    
    // find smallest index out of place
    let start = nums.length - 1;
    let rightPointer = nums[start];
    
    
    for (let i = end, j = start; i < nums.length; i++, j--) {
        if (nums[i] < leftPointer) {
            end = i;
        } else {
            leftPointer = nums[i];
        }
        
        if (nums[j] > rightPointer) {
            start = j;
        } else {
            rightPointer = nums[j];
        }
    }
    
    return end > start ? end - start + 1: 0;
};