feat: 54_spiral_matrix

54_spiral_matrix/main.cpp

@@ -0,0 +1,54 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+   private:
+    // {row, col}
+    const vector<pair<int, int>> directions{
+        {0, 1},
+        {1, 0},
+        {0, -1},
+        {-1, 0},
+    };
+
+    inline pair<int, int> addPair(const pair<int, int>& x, const pair<int, int>& y) {
+        return {x.first + y.first, x.second + y.second};
+    }
+
+    void nextDirection(int& index, pair<int, int>& direction) {
+        if (++index >= 4) index = 0;
+        direction = directions[index];
+    }
+
+   public:
+    vector<int> spiralOrder(vector<vector<int>>& matrix) {
+        const int m = matrix.size();
+        const int n = matrix[0].size();
+
+        vector<int> result;
+
+        vector<vector<bool>> visited(m + 2, vector<bool>(n + 2, false));
+        for (int i = 0; i < m + 2; i++)
+            visited[i][0] = true, visited[i][n + 1] = true;
+        for (int i = 0; i < n + 2; i++)
+            visited[0][i] = true, visited[m + 1][i] = true;
+
+        int directionIndex = 0;
+        pair<int, int> direction = directions[directionIndex];
+
+        pair<int, int> currentPos{1, 1};
+
+        for (int i = 0; i < m * n; i++) {
+            auto nextPos = addPair(currentPos, direction);
+            if (visited[nextPos.first][nextPos.second]) {
+                nextDirection(directionIndex, direction);
+                nextPos = addPair(currentPos, direction);
+            }
+            visited[currentPos.first][currentPos.second] = true;
+            result.emplace_back(matrix[currentPos.first - 1][currentPos.second - 1]);
+            currentPos = nextPos;
+        }
+
+        return result;
+    }
+};