Patching Array

This page explains Java solution to problem Patching Array using Array data structure.

Problem Statement

Given a sorted positive integer array nums and an integer n, add/patch elements to the array such that any number in range [1, n] inclusive can be formed by the sum of existing & patched elements in the array. Return the minimum number of patches required.

Input: nums = [1,3], n = 6
Output: 1
Explanation:
if we add/patch 2 to nums, we can make all the number from 1 to 6, so return 1.

Input: nums = [1,5,10], n = 20
Output: 20

Solution

package com.vc.hard;

class PatchingArray {
    public int minPatches(int[] arr, int n) {
        int missingCount = 0;
        long missing = 1;
        int i = 0;
        while(missing <= n) {
            if(i < arr.length && arr[i] <= missing) {
                missing += arr[i++];
            }
            else {
                missing += missing;
                missingCount++;
            }
        }
        return missingCount;
    }
}

Time Complexity

O(N) Where
N is total number of elements in an input array

Space Complexity

O(1)