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Author: Chris Wu

problems/kth-smallest-element-in-a-sorted-matrix.py

@@ -0,0 +1,14 @@
+class Solution(object):
+    def kthSmallest(self, matrix, k):
+        memo = [0]*len(matrix)
+        opt = []
+        while len(opt)<k:
+            m = float('inf')
+            i_min = None
+            for i, row in enumerate(matrix):
+                if memo[i]<len(matrix) and row[memo[i]]<m:
+                    m = row[memo[i]]
+                    i_min = i
+            opt.append(m)
+            memo[i_min]+=1
+        return opt[-1]

problems/search-a-2d-matrix.py

@@ -0,0 +1,49 @@
+"""
+First I decided to flatten the matrix to an 1-D array, `A`.
+Because it is easier to navigate in this structure.
+And because `A` is already sorted, we can aplly binary search here.
+"""
+class Solution(object):
+    def searchMatrix(self, matrix, target):
+        A = []
+        for row in matrix: A.extend(row)
+
+        l = 0
+        r = len(A)-1
+        while l<=r:
+            m = (l+r)/2
+            if A[l]==target: return True
+            if A[m]==target: return True
+            if A[r]==target: return True
+
+            if A[m]>target:
+                r = m-1
+            else:
+                l = m+1
+        return False
+
+class Solution(object):
+    def searchMatrix(self, matrix, target):
+        def getMatrix(i):
+            n = i/M
+            m = i%M
+            return matrix[n][m]
+
+        if not matrix or len(matrix)==0 or len(matrix[0])==0: return False
+
+        N = len(matrix)
+        M = len(matrix[0])
+
+        l = 0
+        r = N*M-1
+        while l<=r:
+            p = (l+r)/2
+            if getMatrix(l)==target: return True
+            if getMatrix(p)==target: return True
+            if getMatrix(r)==target: return True
+
+            if getMatrix(p)>target:
+                r = p-1
+            else:
+                l = p+1
+        return False