數(shù)組轉(zhuǎn)稀疏數(shù)組

1. 遍歷原始數(shù)組，找出有效數(shù)據(jù)個(gè)數(shù) n；
2. 根據(jù)有效數(shù)據(jù)個(gè)數(shù)，構(gòu)建稀疏數(shù)組 sparseArr = int[n+1][3];
3. 將原始數(shù)組的行數(shù)row、列數(shù)column和有效數(shù)據(jù)個(gè)數(shù)n填入稀疏數(shù)組的第一行 sparseArr[0] =new int[] {row, column, n};
4. 遍歷原始二維數(shù)組，找到有效數(shù)據(jù)依次填入稀疏數(shù)組；

public static int[][] toSparse(int[][] arr, int exclude) {
  int row = arr.length;
  int column = arr[0].length;
  int n = 0;
  for(int  i = 0; i < row; i++) {
    for(int j = 0; j < column; j++) {
      if(arr[i][j] != exclude) {
        n += 1;
      }
    }
  }
  int[][] sparseArr = new int[n+1][3];
  sparseArr[0] = new int[]{row, column, n};
  int t = 1;
  for(int  i = 0; i < row; i++) {
    for(int j = 0; j < column; j++) {
      if(arr[i][j] != exclude) {
        sparseArr[t] = new int[]{i, j, arr[i][j]};
        t += 1;
      }
    }
  }
  return sparseArr;
}

稀疏數(shù)組轉(zhuǎn)數(shù)組

1. 根據(jù)稀疏數(shù)組的sparseArr[0]構(gòu)建二維數(shù)組；
2. 遍歷二維數(shù)組將其初始化為默認(rèn)值；
3. 按行遍歷稀疏數(shù)組，修改二維數(shù)組指定下標(biāo)的數(shù)據(jù)；

public static int[][] restoreArr(int[][] sparseArr, int defaultValue) {
  int row = sparseArr[0][0];
  int column = sparseArr[0][1];
  int[][] arr = new int[row][column];
  if(defaultValue != 0) {
    for(int  i = 0; i < row; i++) {
      for(int j = 0; j < column; j++) {
        arr[i][j] = defaultValue;
      }
    }
  }
  for(int i = 1; i < sparseArr.length; i++) {
    arr[sparseArr[i][0]][sparseArr[i][1]] = sparseArr[i][2];
  }
  return arr;
}