Qualcomm Coding Questions 2025-2026 | Placement Interview Problems with Solutions

Coding Questions - Complete Problem Set

Practice coding interview questions for technology and hardware companies.

Arrays & Strings

1. Two Sum

def two_sum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        if target - num in seen:
            return [seen[target - num], i]
        seen[num] = i
    return []

2. Reverse Linked List

def reverse_list(head):
    prev = None
    while head:
        next_node = head.next
        head.next = prev
        prev = head
        head = next_node
    return prev

3. Binary Search

def binary_search(nums, target):
    left, right = 0, len(nums) - 1
    while left <= right:
        mid = (left + right) // 2
        if nums[mid] == target:
            return mid
        elif nums[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    return -1

4. LRU Cache

from collections import OrderedDict

class LRUCache:
    def __init__(self, capacity):
        self.cache = OrderedDict()
        self.capacity = capacity

    def get(self, key):
        if key not in self.cache:
            return -1
        self.cache.move_to_end(key)
        return self.cache[key]

    def put(self, key, value):
        if key in self.cache:
            self.cache.move_to_end(key)
        self.cache[key] = value
        if len(self.cache) > self.capacity:
            self.cache.popitem(last=False)

5. Valid BST

def is_valid_bst(root, min_val=float('-inf'), max_val=float('inf')):
    if not root:
        return True
    if root.val <= min_val or root.val >= max_val:
        return False
    return (is_valid_bst(root.left, min_val, root.val) and
            is_valid_bst(root.right, root.val, max_val))

6. Number of Islands

def num_islands(grid):
    if not grid:
        return 0
    count = 0
    rows, cols = len(grid), len(grid[0])

    def dfs(r, c):
        if r < 0 or r >= rows or c < 0 or c >= cols or grid[r][c] == '0':
            return
        grid[r][c] = '0'
        dfs(r+1, c)
        dfs(r-1, c)
        dfs(r, c+1)
        dfs(r, c-1)

    for r in range(rows):
        for c in range(cols):
            if grid[r][c] == '1':
                count += 1
                dfs(r, c)
    return count

7. Maximum Subarray

def max_subarray(nums):
    max_sum = current_sum = nums[0]
    for num in nums[1:]:
        current_sum = max(num, current_sum + num)
        max_sum = max(max_sum, current_sum)
    return max_sum

Related Resources

Interview Experience

Real interview experiences.

Preparation Guide

Complete preparation strategy.

---

Practice these problems!

Last updated: February 2026