835. Image Overlap

Author: Partho Biswas

README.md

@@ -157,6 +157,7 @@ I have solved quite a number of problems from several topics. See the below tabl
 |49| **[289. Game of Life](https://tinyurl.com/y5ujyvu5)** | [Python](https://tinyurl.com/wu6rdaw/289_Game_of_Life.py), [Swift](https://tinyurl.com/wuja3c4/289_Game_of_Life.swift)| --- | Medium | --- |
 |50| **[54. Spiral Matrix](https://tinyurl.com/yy5rnvce)** | [Python](https://tinyurl.com/wu6rdaw/54_Spiral_Matrix.py), [Swift](https://tinyurl.com/wuja3c4/54_Spiral_Matrix.swift)| [Official](https://tinyurl.com/s6np53k) | Medium | --- |
 |51| **[380. Insert Delete GetRandom O(1)](https://tinyurl.com/y3urnkfj)** | [Python](https://tinyurl.com/wu6rdaw/380_Insert_Delete_GetRandom_O(1).py), [Swift](https://tinyurl.com/wuja3c4/380_Insert_Delete_GetRandom_O(1).swift)| [Official](https://tinyurl.com/t4t38od) | Medium | --- |
+|52| **[835. Image Overlap](https://tinyurl.com/r9x9nkm)** | [Python](https://tinyurl.com/wu6rdaw/835_Image_Overlap.py), [Swift](https://tinyurl.com/wuja3c4/835_Image_Overlap.swift)| [Art 1](https://tinyurl.com/tx3gd98), [Art 2](https://tinyurl.com/tnmj6du) | Medium | --- |
 
 
 </p>

leetcode.com/python/743_Network_Delay_Time.py

@@ -3,7 +3,7 @@
 from collections import defaultdict
 
 # """
-# Source: https://tinyurl.com/rmcr2xk. Uses simple DFS - Accepted
+# Source: https://tinyurl.com/rmcr2xk. Uses simple DFS - Time Limit Exceeded
 class Solution(object):
     def networkDelayTime(self, times, N, K):
         graph = defaultdict(list)
@@ -15,7 +15,7 @@ def networkDelayTime(self, times, N, K):
         return totalTime if totalTime < float("inf") else -1
 
     def DFS(self, graph, distance, node, elapsedTimeSoFar):
-        if elapsedTimeSoFar >= distance[node]:
+        if elapsedTimeSoFar >= distance[node]:  # Here we are essentially checking if our existing/already calculated disstance is grater than out current culculated time. If our current path is greated than already traverssed path then this path is't going to give us any better solution. so we leave this path.
             return
         distance[node] = elapsedTimeSoFar
         for neighbour, time in sorted(graph[node]):
@@ -24,7 +24,7 @@ def DFS(self, graph, distance, node, elapsedTimeSoFar):
 
 
 # """
-# Source: https://tinyurl.com/vbetlaq. Uses simple BFS - Accepted
+# Source: https://tinyurl.com/vbetlaq. Uses simple BFS - Accepted. Here BFS if preferable over DFS
 class Solution:
     def networkDelayTime(self, times, N, K):
         elapsedTime, graph, queue = [0] + [float("inf")] * N, defaultdict(list), deque([(0, K)])

leetcode.com/python/835_Image_Overlap.py

@@ -0,0 +1,22 @@
+from collections import defaultdict
+class Solution(object):
+    def largestOverlap(self, A, B):
+        """
+        :type A: List[List[int]]
+        :type B: List[List[int]]
+        :rtype: int
+        """
+        translationDistanceCount = defaultdict(int)
+        a1Coordinates, b1Coordinates = [], []
+        for i in range(len(A)):
+            for j in range(len(A[0])):
+                if A[i][j] == 1:
+                    a1Coordinates.append((i, j))
+                if B[i][j] == 1:
+                    b1Coordinates.append((i, j))
+
+        for aRow, aCol in a1Coordinates:
+            for bRow, bCol in b1Coordinates:
+                translation = (bRow - aRow, bCol - aCol)
+                translationDistanceCount[translation] += 1
+        return max(translationDistanceCount.values()) if translationDistanceCount else 0