Amazon Coding Questions - DSA Problems & Solutions

Company Overview

This page contains Amazon coding questions from Amazon OA placement papers with detailed solutions.

Coding Focus

Amazon OA coding section includes 2 problems focusing on DSA. Master graphs, sliding window, bit manipulation, and dynamic programming to succeed.

Amazon Coding Questions Overview

Amazon OA Coding Section:

• Problems: 2 coding problems
• Time: 90 minutes total
• Languages: Java, C++, Python

Coding Problems

Question 1: Two Sum

Q1: Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

Solution (Java):

public int[] twoSum(int[] nums, int target) {
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < nums.length; i++) {
        int complement = target - nums[i];
        if (map.containsKey(complement)) {
            return new int[]{map.get(complement), i};
        }
        map.put(nums[i], i);
    }
    return new int[]{};
}

Time Complexity: O(n)

Question 2: Longest Substring Without Repeating Characters

Q2: Find the length of the longest substring without repeating characters.

Solution (Java):

public int lengthOfLongestSubstring(String s) {
    Map<Character, Integer> map = new HashMap<>();
    int maxLen = 0;
    int left = 0;

    for (int right = 0; right < s.length(); right++) {
        char c = s.charAt(right);
        if (map.containsKey(c) && map.get(c) >= left) {
            left = map.get(c) + 1;
        }
        map.put(c, right);
        maxLen = Math.max(maxLen, right - left + 1);
    }

    return maxLen;
}

Time Complexity: O(n)

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