# 64 ms straight forward c++ DFS solution, beat 100%

• First round of code submission.

``````class Solution {
int mMaxLen, mTracker;
int m, n;
void dfs(vector<vector<int>>& matrix, vector<vector<int>>& memo, int i, int j) {
if (memo[i][j] != 0) {
mTracker = max(mTracker, memo[i][j]);
return;
} else {
mTracker = 0;
if (i > 0 && matrix[i][j] < matrix[i-1][j]) {
dfs(matrix, memo, i-1, j);
memo[i][j] = max(memo[i][j], mTracker + 1);
}
if (i < m - 1 && matrix[i][j] < matrix[i+1][j]) {
dfs(matrix, memo, i+1, j);
memo[i][j] = max(memo[i][j], mTracker + 1);
}
if (j > 0 && matrix[i][j] < matrix[i][j-1]) {
dfs(matrix, memo, i, j-1);
memo[i][j] = max(memo[i][j], mTracker + 1);
}
if (j < n - 1 && matrix[i][j] < matrix[i][j+1]) {
dfs(matrix, memo, i, j+1);
memo[i][j] = max(memo[i][j], mTracker + 1);
}
}
mTracker = max(++mTracker, memo[i][j]);
memo[i][j] = max(memo[i][j], mTracker);
mMaxLen = max(mTracker, mMaxLen);
}
public:
int longestIncreasingPath(vector<vector<int>>& matrix) {
if (matrix.empty()) {
return 0;
}
m = matrix.size();
n = matrix[0].size();
vector<vector<int>> memo(m, vector<int>(n, 0));
mMaxLen = 0; mTracker = 0;
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
if (memo[i][j] == 0) {
dfs(matrix, memo, i, j);
}
}
}
/** uncomment to display memo walk route
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
cout << memo[i][j] << ' ';
}
cout << '\n';
}
*/
return mMaxLen;
}
};``````

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