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073_set-matrix-zeroes.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#@author: rye
+#@time: 2019/3/20
+
+class Solution(object):
+    def setZeroes(self, matrix):
+        """
+        :type matrix: List[List[int]]
+        :rtype: None Do not return anything, modify matrix in-place instead.
+        """
+
+        row = len(matrix)
+        col = len(matrix[0])
+
+        res = []
+        for i in range(row):
+            for j in range(col):
+                if matrix[i][j] == 0:
+                    res.append([i, j])
+        for k in res:
+            for k1 in range(col):
+                matrix[k[0]][k1] = 0
+            for k2 in range(row):
+                matrix[k2][k[1]] = 0
+
+        return matrix
+
+# 大佬的代码
+'''
+思想：https://github.com/ryeLearnMore/awesome-algorithm/blob/master/docs/Leetcode_Solutions/Python/073.%20Set%20Matrix%20Zeroes.md
+一边遍历，一边将相应的行和列置为0是行不通的，会影响后面元素的遍历判断，
+所以要记录下哪些行和哪些列是要置为0的。为了节约空间，在原矩阵中借两条边，如果该行或者列要置为0，
+则把左边或者上边的相应位置置为0。如果左边和上边本来就有0，那么需要额外标记一下，最后把左边或者右边也全部置为0.
+'''
+class Solution1(object):
+    def setZeroes(self, matrix):
+        if len(matrix) == 0:
+            return
+
+        colFlag, rowFlag, rows, cols = 1, 1, len(matrix), len(matrix[0])
+
+        # Recording whether the first row and the first col contain 0
+        for i in range(cols):
+            if matrix[0][i] == 0:
+                colFlag = 0
+
+        for i in range(rows):
+            if matrix[i][0] == 0:
+                rowFlag = 0
+
+        # Start from the second row and the second col
+        for i in range(1, rows):
+            for j in range(1, cols):
+                if matrix[i][j] == 0:
+                    matrix[i][0] = matrix[0][j] = 0
+
+        # Set zero from the bottom
+        for i in range(rows - 1, 0, -1):
+            for j in range(cols - 1, 0, -1):
+                if matrix[i][0] == 0 or matrix[0][j] == 0:
+                    matrix[i][j] = 0
+
+        # Check the row and the col
+        if colFlag == 0:
+            for i in range(cols):
+                matrix[0][i] = 0
+        if rowFlag == 0:
+            for i in range(rows):
+                matrix[i][0] = 0
+
+if __name__ == '__main__':
+    matrix = [
+        [1, 1, 1],
+        [1, 0, 1],
+        [1, 1, 1]
+    ]
+    print(Solution().setZeroes(matrix))