首页 > 代码库 > Set Matrix Zeroes

Set Matrix Zeroes

2024-07-10 02:33:00   227人阅读

题目

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

Follow up:

Did you use extra space?
A straight forward solution using O(mn) 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?

方法

空间复杂度要求为O(1)，肯定需要考虑如何使用数组本身，使用数组的第一行和第一列作为标记。
    public void setZeroes(int[][] matrix) {
        if (!(matrix == null || matrix.length == 0 || matrix[0].length == 0)) {
            int lenI = matrix.length;
            int lenJ = matrix[0].length;
            boolean rowFirst = false;
            boolean colFirst = false;
            for (int i = 0; i < lenI; i++) {
                if (matrix[i][0] == 0) {
                    colFirst = true;
                    break;
                }
            }
            
            for (int j = 0; j < lenJ; j++) {
                if (matrix[0][j] == 0) {
                    rowFirst = true;
                    break;
                }
            }
            
            for (int i = 0; i < lenI; i++) {
                for (int j = 0; j < lenJ; j++) {
                    if (matrix[i][j] == 0) {
                        matrix[i][0] = 0;
                        matrix[0][j] = 0;
                    }
                }
            }
            for (int i = 1; i < lenI; i++) {
                if (matrix[i][0] == 0) {
                    for (int j = 1; j < lenJ; j++) {
                        matrix[i][j] = 0;
                    }
                }
            }
            
            for (int j = 1; j < lenJ; j++) {
                if (matrix[0][j] == 0) {
                    for (int i = 1; i < lenI; i++) {
                        matrix[i][j] = 0;
                    }
                }
            }
            
            if (rowFirst) {
                for (int j = 0; j < lenJ; j++) {
                    matrix[0][j] = 0;
                }
            }
            
            if (colFirst) {
                for (int i = 0; i < lenI; i++) {
                    matrix[i][0] = 0;
                }
            }
        }
    }


联系
我们