算法：矩阵置零_矩阵置零算法封装

 题目：

给定一个 m x n 的矩阵，如果一个元素为 0，则将其所在行和列的所有元素都设为 0。请使用原地算法。

示例 1:

输入: 
[
  [1,1,1],
  [1,0,1],
  [1,1,1]
]
输出: 
[
  [1,0,1],
  [0,0,0],
  [1,0,1]
]

矩阵置0，要求常数空间
 
//额外存储空间
class Solution {
  public void setZeroes(int[][] matrix) {
    //行
    int R = matrix.length;
    //列
    int C = matrix[0].length;
    Set<Integer> rows = new HashSet<Integer>();
    Set<Integer> cols = new HashSet<Integer>();
 
    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        if (matrix[i][j] == 0) {
          //记下对应行和列
          rows.add(i);
          cols.add(j);
        }
      }
    }
 
    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        if (rows.contains(i) || cols.contains(j)) {
          matrix[i][j] = 0;
        }
      }
    }
 
  }
}
 
//O(1)空间的暴力
class Solution {
  public void setZeroes(int[][] matrix) {
    int MODIFIED = -1000000;
    //行
    int R = matrix.length;
    //列
    int C = matrix[0].length;
 
    for (int r = 0; r < R; r++) {
      for (int c = 0; c < C; c++) {
        if (matrix[r][c] == 0) {
          for (int k = 0; k < C; k++) {
            if (matrix[r][k] != 0) {
              matrix[r][k] = MODIFIED;
            }
          }
          for (int k = 0; k < R; k++) {
            if (matrix[k][c] != 0) {
              matrix[k][c] = MODIFIED;
            }
          }
        }
      }
    }
 
    for (int r = 0; r < R; r++) {
      for (int c = 0; c < C; c++) {
        if (matrix[r][c] == MODIFIED) {
          matrix[r][c] = 0;
        }
      }
    }
 
  }
}
 
class Solution {
  public void setZeroes(int[][] matrix) {
    Boolean isCol = false;
    int R = matrix.length;
    int C = matrix[0].length;
 
    for (int i = 0; i < R; i++) {
      if (matrix[i][0] == 0) {
        isCol = true;
      }
 
      for (int j = 1; j < C; j++) {
        if (matrix[i][j] == 0) {
          matrix[0][j] = 0;
          matrix[i][0] = 0;
        }
      }
    }
 
    for (int i = 1; i < R; i++) {
      for (int j = 1; j < C; j++) {
        if (matrix[i][0] == 0 || matrix[0][j] == 0) {
          matrix[i][j] = 0;
        }
      }
    }
 
    if (matrix[0][0] == 0) {
      for (int j = 0; j < C; j++) {
        matrix[0][j] = 0;
      }
    }
 
    if (isCol) {
      for (int i = 0; i < R; i++) {
        matrix[i][0] = 0;
      }
    }
 
  }
}

参考链接：https://leetcode-cn.com/problems/set-matrix-zeroes/solution/ju-zhen-zhi-ling-by-leetcode/