setZeroes.cpp

class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size(), n = matrix[0].size();
        unordered_set<int> row, col;
        for (int i = 0; i < m; ++i) {
            for (int j = 0; j < n; ++j) {
                if (!matrix[i][j]) {
                    row.insert(i);
                    col.insert(j);
                }
            }
        }
        for (int r: row) {
            for (int i = 0; i < n; ++i) {
                matrix[r][i] = 0;
            }
        }
        for (int c: col) {
            for (int i = 0; i < m; ++i) {
                matrix[i][c] = 0;
            }
        }
    }
};

// O(1) Space
class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size(), n = matrix[0].size();
        bool i0 = false, j0 = false;
        
        // 第一行是否包含 0
        for (int j = 0; j < n; ++j) {
            if (matrix[0][j] == 0) {
                i0 = true;
                break;
            }
        }

        // 第一列是否包含 0
        for (int i = 0; i < m; ++i) {
            if (matrix[i][0] == 0) {
                j0 = true;
                break;
            }
        }
        for (int i = 1; i < m; ++i) {
            for (int j = 1; j < n; ++j) {
                if (matrix[i][j] == 0) {
                    matrix[i][0] = 0;
                    matrix[0][j] = 0;
                }
            }
        }
        for (int i = 1; i < m; ++i) {
            for (int j = 1; j < n; ++j) {
                if (matrix[i][0] == 0 || matrix[0][j] == 0) {
                    matrix[i][j] = 0;
                }
            }
        }
        if (i0) {
            for (int j = 0; j < n; ++j) {
                matrix[0][j] = 0;
            }
        }
        if (j0) {
            for (int i = 0; i < m; ++i) {
                matrix[i][0] = 0;
            }
        }
    }
};

// 作者：lcbin
// 链接：https://leetcode.cn/problems/zero-matrix-lcci/solution/-by-lcbin-n12y/
// 来源：力扣（LeetCode）
// 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。