数据结构与算法（一）稀疏数组

数据结构与算法（一）稀疏数组

应用场景

放一个数据中大部分元素是0，或者同一个值的数组时，可以使用稀疏数组来保存该数组

处理方式

记录数组一共有几行几列，有多少不同的值 2.把具有不同值的元素的行列以即值记录在小规模的数组中。

例子 代码

public class SparseArray {
          
   

    public static void main(String[] args) {
          
   
        int[][] chessArrayOld = new int[6][7];
        chessArrayOld[0][3] = 22;
        chessArrayOld[0][6] = 15;
        chessArrayOld[1][1] = 11;
        chessArrayOld[1][5] = 17;
        chessArrayOld[2][3] = -6;
        chessArrayOld[3][5] = 39;
        chessArrayOld[4][0] = 91;
        chessArrayOld[5][2] = 28;
        System.out.println("Original Array-----------------------------------");

        for (int i = 0; i < chessArrayOld.length; i++) {
          
   
            for(int j = 0; j< chessArrayOld[0].length; j++){
          
   
                System.out.printf("%d	", chessArrayOld[i][j]);
            }
            System.out.println();
        }

        int[][] sparseArray = chessToSparse(chessArrayOld);

        System.out.println("Sparse Array-----------------------------------");

        for (int i = 0; i < sparseArray.length; i++) {
          
   
            for(int j = 0; j< sparseArray[0].length; j++){
          
   
                System.out.printf("%d	", sparseArray[i][j]);
            }
            System.out.println();
        }

        int[][] chessArrayNew = sparseToChess(sparseArray);

        System.out.println("New Array-----------------------------------");

        for (int i = 0; i < chessArrayNew.length; i++) {
          
   
            for(int j = 0; j< chessArrayNew[0].length; j++){
          
   
                System.out.printf("%d	", chessArrayNew[i][j]);
            }
            System.out.println();
        }

    }

    private static int[][] sparseToChess(int[][] sparseArray) {
          
   
        int[][] chessArray = new int[sparseArray[0][0]][sparseArray[0][1]];
        int sum = sparseArray[0][2];
        for (int i = 1; i < sum + 1; i++) {
          
   
            chessArray[sparseArray[i][0]][sparseArray[i][1]] = sparseArray[i][2];
        }
        return chessArray;
    }

    private static int[][] chessToSparse(int[][] chessArrayOld) {
          
   
        //get the total number of non-zero
        int sum = 0;
        for (int i = 0; i < chessArrayOld.length; i++) {
          
   
            for (int j = 0; j < chessArrayOld[0].length; j++) {
          
   
                if (chessArrayOld[i][j] != 0){
          
   
                    sum++;
                }
            }
        }

        int[][] sparseArray = new int[sum+1][3];

        sparseArray[0][0] = chessArrayOld.length;
        sparseArray[0][1] = chessArrayOld[0].length;
        sparseArray[0][2] = sum;

        int count = 0;
        for (int i = 0; i < chessArrayOld.length; i++) {
          
   
            for (int j = 0; j < chessArrayOld[0].length; j++) {
          
   
                if (chessArrayOld[i][j] != 0){
          
   
                    count = count + 1;
                    sparseArray[count][0] = i;
                    sparseArray[count][1] = j;
                    sparseArray[count][2] = chessArrayOld[i][j];
                }
            }
        }

        return sparseArray;

    }
}