Given an integer matrix, find the length of the longest increasing path.
From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed).
Example 1:
nums = [ [9,9,4], [6,6,8], [2,1,1] ]
Return 4
The longest increasing path is [1, 2, 6, 9]
.
Example 2:
nums = [ [3,4,5], [3,2,6], [2,2,1] ]
Return 4
The longest increasing path is [3, 4, 5, 6]
. Moving diagonally is not allowed.
int x_1[4] = { 1, -1, 0, 0 }; int y_1[4] = { 0, 0, -1, 1 }; int dfs(vector<vector<int>>& matrix,int rows,int cols, int row, int col, vector<vector<int>>&dp) { if (dp[row][col]) return dp[row][col]; int maxDepth = 1; for (int i = 0; i < 4; ++i) { int x = row + x_1[i]; int y = col + y_1[i]; if (x < 0 || y < 0 || x >= rows || y >= cols || matrix[x][y] <= matrix[row][col]) continue; int len = dfs(matrix, rows, cols, x, y, dp) + 1; if (maxDepth < len) maxDepth = len; } dp[row][col] = maxDepth; return maxDepth; } int longestIncreasingPath(vector<vector<int>>& matrix) { if (matrix.empty()) return 0; int rows = matrix.size(); int cols = matrix[0].size(); vector<vector<int>> dp(rows, vector<int>(cols, 0)); int maxDepth = 1; for (int i = 0; i < rows; ++i) { for (int j = 0; j < cols; ++j) { int tmp = dfs(matrix,rows,cols, i, j, dp); if (maxDepth < tmp) maxDepth = tmp; } } return maxDepth; }