Create reshape-the-matrix.py

Author: kamyu104

Python/reshape-the-matrix.py

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+# Time:  O(m * n)
+# Space: O(m * n)
+
+# In MATLAB, there is a very useful function called 'reshape',
+# which can reshape a matrix into a new one with different size but keep its original data.
+#
+# You're given a matrix represented by a two-dimensional array,
+# and two positive integers r and c representing the row number
+# and column number of the wanted reshaped matrix, respectively.
+#
+# The reshaped matrix need to be filled with
+# all the elements of the original matrix in the same row-traversing order as they were.
+#
+# If the 'reshape' operation with given parameters is possible and legal,
+# output the new reshaped matrix; Otherwise, output the original matrix.
+#
+# Example 1:
+# Input: 
+# nums = 
+# [[1,2],
+#  [3,4]]
+# r = 1, c = 4
+# Output: 
+# [[1,2,3,4]]
+# Explanation:
+# The row-traversing of nums is [1,2,3,4]. The new reshaped matrix is a 1 * 4 matrix,
+# fill it row by row by using the previous list.
+#
+# Example 2:
+# Input: 
+# nums = 
+# [[1,2],
+#  [3,4]]
+# r = 2, c = 4
+# Output: 
+# [[1,2],
+#  [3,4]]
+# Explanation:
+# There is no way to reshape a 2 * 2 matrix to a 2 * 4 matrix. So output the original matrix.
+#
+# Note:
+# The height and width of the given matrix is in range [1, 100].
+# The given r and c are all positive.
+
+class Solution(object):
+    def matrixReshape(self, nums, r, c):
+        """
+        :type nums: List[List[int]]
+        :type r: int
+        :type c: int
+        :rtype: List[List[int]]
+        """
+        if not nums or \
+           r*c != len(nums) * len(nums[0]):
+            return nums
+
+        result = [[0 for _ in xrange(c)] for _ in xrange(r)]
+        count = 0
+        for i in xrange(len(nums)):
+            for j in xrange(len(nums[0])):
+                result[count/c][count%c] = nums[i][j]
+                count += 1
+        return result