0073. Set Matrix Zeroes

Author: coderbean

markdown/0073. Set Matrix Zeroes.md

@@ -0,0 +1,84 @@
+### [73\. Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes/)
+
+Difficulty: **Medium**
+
+
+Given a _m_ x _n_ matrix, if an element is 0, set its entire row and column to 0\. Do it .
+
+**Example 1:**
+
+```
+Input: 
+[
+  [1,1,1],
+  [1,0,1],
+  [1,1,1]
+]
+Output: 
+[
+  [1,0,1],
+  [0,0,0],
+  [1,0,1]
+]
+```
+
+**Example 2:**
+
+```
+Input: 
+[
+  [0,1,2,0],
+  [3,4,5,2],
+  [1,3,1,5]
+]
+Output: 
+[
+  [0,0,0,0],
+  [0,4,5,0],
+  [0,3,1,0]
+]
+```
+
+**Follow up:**
+
+*   A straight forward solution using O(_m__n_) space is probably a bad idea.
+*   A simple improvement uses O(_m_ + _n_) space, but still not the best solution.
+*   Could you devise a constant space solution?
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public void setZeroes(int[][] matrix) {
+        int row0 = 1;
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[0].length; j++) {
+                if (matrix[i][j] == 0) {
+                    if (i == 0) {
+                        row0 = 0;
+                    } else {
+                        matrix[i][0] = 0;
+                    }
+                    matrix[0][j] = 0; // 表示第 j 列
+                }
+            }
+        }
+        for (int i = matrix.length - 1; i >= 1; i--) {
+            for (int j = matrix[0].length - 1; j >= 0; j--) {
+                if (matrix[0][j] == 0 || matrix[i][0] == 0) {
+                    matrix[i][j] = 0;
+                }
+            }
+        }
+        if (row0 == 0) {
+            for (int i = 0; i < matrix[0].length; i++) {
+                matrix[0][i] = 0;
+            }
+        }
+    }
+}
+```
+![](https://raw.githubusercontent.com/PicGoBed/PicBed/master/20190722143115.png)

src/main/java/leetcode/_73_/Main.java

@@ -0,0 +1,26 @@
+package leetcode._73_;
+
+import leetcode.common.Printer;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        // int[][] matrix = {
+        //         {1, 1, 1},
+        //         {1, 0, 1},
+        //         {1, 1, 1}};
+        int[][] martix = {{0, 1, 2, 0}, {3, 4, 5, 2}, {1, 3, 1, 5}};
+        Printer.printArrays(martix);
+        solution.setZeroes(martix);
+        Printer.printArrays(martix);
+
+
+        int[][] martix2 = {{1,0,3}};
+        solution.setZeroes(martix2);
+        Printer.printArrays(martix2);
+    }
+}
+

src/main/java/leetcode/_73_/Solution.java

@@ -0,0 +1,31 @@
+package leetcode._73_;
+
+class Solution {
+    public void setZeroes(int[][] matrix) {
+        int row0 = 1;
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[0].length; j++) {
+                if (matrix[i][j] == 0) {
+                    if (i == 0) {
+                        row0 = 0;
+                    } else {
+                        matrix[i][0] = 0;
+                    }
+                    matrix[0][j] = 0; // 表示第 j 列
+                }
+            }
+        }
+        for (int i = matrix.length - 1; i >= 1; i--) {
+            for (int j = matrix[0].length - 1; j >= 0; j--) {
+                if (matrix[0][j] == 0 || matrix[i][0] == 0) {
+                    matrix[i][j] = 0;
+                }
+            }
+        }
+        if (row0 == 0) {
+            for (int i = 0; i < matrix[0].length; i++) {
+                matrix[0][i] = 0;
+            }
+        }
+    }
+}

src/main/java/leetcode/_73_/solution.md

@@ -0,0 +1,84 @@
+### [73\. Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes/)
+
+Difficulty: **Medium**
+
+
+Given a _m_ x _n_ matrix, if an element is 0, set its entire row and column to 0\. Do it .
+
+**Example 1:**
+
+```
+Input: 
+[
+  [1,1,1],
+  [1,0,1],
+  [1,1,1]
+]
+Output: 
+[
+  [1,0,1],
+  [0,0,0],
+  [1,0,1]
+]
+```
+
+**Example 2:**
+
+```
+Input: 
+[
+  [0,1,2,0],
+  [3,4,5,2],
+  [1,3,1,5]
+]
+Output: 
+[
+  [0,0,0,0],
+  [0,4,5,0],
+  [0,3,1,0]
+]
+```
+
+**Follow up:**
+
+*   A straight forward solution using O(_m__n_) space is probably a bad idea.
+*   A simple improvement uses O(_m_ + _n_) space, but still not the best solution.
+*   Could you devise a constant space solution?
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public void setZeroes(int[][] matrix) {
+        int row0 = 1;
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[0].length; j++) {
+                if (matrix[i][j] == 0) {
+                    if (i == 0) {
+                        row0 = 0;
+                    } else {
+                        matrix[i][0] = 0;
+                    }
+                    matrix[0][j] = 0; // 表示第 j 列
+                }
+            }
+        }
+        for (int i = matrix.length - 1; i >= 1; i--) {
+            for (int j = matrix[0].length - 1; j >= 0; j--) {
+                if (matrix[0][j] == 0 || matrix[i][0] == 0) {
+                    matrix[i][j] = 0;
+                }
+            }
+        }
+        if (row0 == 0) {
+            for (int i = 0; i < matrix[0].length; i++) {
+                matrix[0][i] = 0;
+            }
+        }
+    }
+}
+```
+![](https://raw.githubusercontent.com/PicGoBed/PicBed/master/20190722143115.png)

src/main/java/leetcode/common/Printer.java

@@ -15,4 +15,23 @@ public static void printArrays(int[] arrays) {
         }
         System.out.print(arrays[arrays.length - 1] + "]");
     }
+
+    public static void printArrays(int[][] arrays) {
+        if (arrays == null) {
+            System.out.println("[]");
+            return;
+        }
+        System.out.print("[\n");
+        for (int i = 0; i < arrays.length; i++) {
+            System.out.print("\t[");
+            for (int j = 0; j < arrays[0].length; j++) {
+                System.out.print(arrays[i][j]);
+                if (j != arrays[0].length - 1) {
+                    System.out.print(",");
+                }
+            }
+            System.out.println("]");
+        }
+        System.out.println("]");
+    }
 }