leetcode

Set Matrix Zeroes

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

Solution1:

better

  public void setZeroes(int[][] matrix) {    int col0 = 1;    int rows = matrix.length;    int cols = matrix[0].length;    for (int i = 0; i < rows; i++) {      if (matrix[i][0] == 0)        col0 = 0;      for (int j = 1; j < cols; j++) {        if (matrix[i][j] == 0) {          matrix[i][0] = 0;          matrix[0][j] = 0;        }      }    }    for (int i = rows - 1; i >= 0; i--) {      for (int j = cols - 1; j >= 1; j--) {        if (matrix[i][0] == 0 || matrix[0][j] == 0) {          matrix[i][j] = 0;        }      }      if (col0 == 0)        matrix[i][0] = 0;    }  }

Solution2:

  public void setZeroes(int[][] matrix) {    boolean fr = false;    boolean fc = false;    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)            fr = true;          if (j == 0)            fc = true;          matrix[0][j] = 0;          matrix[i][0] = 0;        }      }    }    for (int i = 1; i < matrix.length; i++) {      for (int j = 1; j < matrix[0].length; j++) {        if (matrix[i][0] == 0 || matrix[0][j] == 0) {          matrix[i][j] = 0;        }      }    }    if (fr) {      for (int j = 0; j < matrix[0].length; j++) {        matrix[0][j] = 0;      }    }    if (fc) {      for (int i = 0; i < matrix.length; i++) {        matrix[i][0] = 0;      }    }  }