// Google-frequency coding patterns in Kotlin // 1. Sliding Window — Max sum of subarray of size K fun maxSumSubarray(arr: IntArray, k: Int): Int { var windowSum = arr.slice(0 until k).sum() var maxSum = windowSum for (i in k until arr.size) { windowSum += arr[i] - arr[i - k] maxSum = maxOf(maxSum, windowSum) } return maxSum } // 2. Two Pointers — Container with most water fun maxArea(height: IntArray): Int { var left = 0 var right = height.lastIndex var maxWater = 0 while (left < right) { val water = minOf(height[left], height[right]) * (right - left) maxWater = maxOf(maxWater, water) if (height[left] < height[right]) left++ else right-- } return maxWater } // 3. BFS — Shortest path in unweighted graph fun shortestPath(graph: Map>, start: Int, end: Int): Int { val queue: Queue> = LinkedList() val visited = mutableSetOf(start) queue.add(start to 0) while (queue.isNotEmpty()) { val (node, dist) = queue.poll() if (node == end) return dist for (neighbor in graph[node] ?: emptyList()) { if (neighbor !in visited) { visited.add(neighbor) queue.add(neighbor to dist + 1) } } } return -1 } // 4. Dynamic Programming — Longest Increasing Subsequence fun lengthOfLIS(nums: IntArray): Int { // Patience sorting — O(n log n) val tails = mutableListOf() for (num in nums) { val pos = tails.binarySearch(num).let { if (it < 0) -(it + 1) else it } if (pos == tails.size) tails.add(num) else tails[pos] = num } return tails.size } // 5. Monotonic Stack — Next greater element fun nextGreaterElements(nums: IntArray): IntArray { val result = IntArray(nums.size) { -1 } val stack = ArrayDeque() // indices for (i in nums.indices) { while (stack.isNotEmpty() && nums[stack.last()] < nums[i]) { result[stack.removeLast()] = nums[i] } stack.addLast(i) } return result }

Phase 9: DSA for Google Interviews

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Senior-Level DSA Topics for Google

Pattern Recognition & Problem-Solving Strategy

Mock Coding Interview Simulation

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