题解 | #矩阵最长递增路径#

参考：https://leetcode-cn.com/problems/fpTFWP/solution/zui-chang-di-zeng-lu-jing-by-leetcode-so-1chr/

class Solution {
private:
    static constexpr int dirs[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    int rows, columns;
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     * 递增路径的最大长度
     * @param matrix int整型vector<vector<>> 描述矩阵的每个数
     * @return int整型
     */
    int solve(vector<vector<int> >& matrix) {
        // write code here
        if (matrix.size() == 0 || matrix[0].size() == 0) {
            return 0;
        }
        rows = matrix.size();
        columns = matrix[0].size();
        auto memo = vector< vector<int>> (rows, vector <int> (columns));
        int ans = 0;
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < columns; ++j) {
                ans = max(ans, dfs(matrix, i, j, memo));
            }
        }
        return ans;
    }

    int dfs(vector< vector<int> > &matrix, int row, int column, vector< vector<int> > &memo) {
        if (memo[row][column] != 0) {
            return memo[row][column];
        }
        ++memo[row][column];
        for (int i = 0; i < 4; ++i) {
            int newRow = row + dirs[i][0], newColumn = column + dirs[i][1];
            if (newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns && matrix[newRow][newColumn] > matrix[row][column]) {
                memo[row][column] = max(memo[row][column], dfs(matrix, newRow, newColumn, memo) + 1);
            }
        }
        return memo[row][column];
    }
    
};