In-Place Move Zeros to End of List - Amazon Top Interview Questions

Problem Statement :

Given a list of integers nums, put all the zeros to the back of the list by modifying the list in-place. The relative ordering of other elements should stay the same.

Can you do it in \mathcal{O}(1)O(1) additional space?


0 ≤ n ≤ 100,000 where n is the length of nums

Example 1

nums = [0, 1, 0, 2, 3]

[1, 2, 3, 0, 0]

Note that [1, 2, 3] appear in the same order as in the input.

Solution :


                        Solution in C++ :

vector<int> solve(vector<int>& nums) {
    int count = 0;

    for (int i = 0; i < nums.size(); ++i) {
        if (nums[i] != 0) {
            swap(nums[i], nums[count]);

                        Solution in Java :

class Solution {
    public int[] solve(int[] nums) {
        int i = 0, j = 0;
        while (j < nums.length) {
            if (nums[j] == 0)
                swap(nums, i++, j++);
        return nums;
    public void swap(int[] a, int i, int j) {
        if (i == j)
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp;

                        Solution in Python : 
class Solution:
    def solve(self, nums):
        j = 0
        for i in range(len(nums)):
            if nums[i] != 0:
                if j != i:
                    nums[j], nums[i] = nums[i], nums[j]
                j += 1

        return nums

View More Similar Problems

Minimum Average Waiting Time

Tieu owns a pizza restaurant and he manages it in his own way. While in a normal restaurant, a customer is served by following the first-come, first-served rule, Tieu simply minimizes the average waiting time of his customers. So he gets to decide who is served first, regardless of how sooner or later a person comes. Different kinds of pizzas take different amounts of time to cook. Also, once h

View Solution →

Merging Communities

People connect with each other in a social network. A connection between Person I and Person J is represented as . When two persons belonging to different communities connect, the net effect is the merger of both communities which I and J belongs to. At the beginning, there are N people representing N communities. Suppose person 1 and 2 connected and later 2 and 3 connected, then ,1 , 2 and 3 w

View Solution →

Components in a graph

There are 2 * N nodes in an undirected graph, and a number of edges connecting some nodes. In each edge, the first value will be between 1 and N, inclusive. The second node will be between N + 1 and , 2 * N inclusive. Given a list of edges, determine the size of the smallest and largest connected components that have or more nodes. A node can have any number of connections. The highest node valu

View Solution →

Kundu and Tree

Kundu is true tree lover. Tree is a connected graph having N vertices and N-1 edges. Today when he got a tree, he colored each edge with one of either red(r) or black(b) color. He is interested in knowing how many triplets(a,b,c) of vertices are there , such that, there is atleast one edge having red color on all the three paths i.e. from vertex a to b, vertex b to c and vertex c to a . Note that

View Solution →

Super Maximum Cost Queries

Victoria has a tree, T , consisting of N nodes numbered from 1 to N. Each edge from node Ui to Vi in tree T has an integer weight, Wi. Let's define the cost, C, of a path from some node X to some other node Y as the maximum weight ( W ) for any edge in the unique path from node X to Y node . Victoria wants your help processing Q queries on tree T, where each query contains 2 integers, L and

View Solution →


We're going to make our own Contacts application! The application must perform two types of operations: 1 . add name, where name is a string denoting a contact name. This must store name as a new contact in the application. find partial, where partial is a string denoting a partial name to search the application for. It must count the number of contacts starting partial with and print the co

View Solution →