feat : spiral-matrix

Author: ekgns33

spiral-matrix/ekgns33.java

@@ -0,0 +1,42 @@
+/*
+*.      lr ->
+*   ^   1 2 3 4. rd
+*   lu  5 6 7 8. v
+*        <-  rl
+* tc : O(mn)
+* sc : O(1)
+* */
+
+class Solution {
+  public List<Integer> spiralOrder(int[][] matrix) {
+    int m = matrix.length;
+    int n = matrix[0].length;
+    int lr = 0, rd = 0, rl = n -1, lu = m - 1;
+    int cnt = 0, target = m*n;
+    List<Integer> res = new ArrayList<>();
+
+    while(lr <= rl && rd <= lu) {
+      for(int startLeft = lr; startLeft <= rl; startLeft++) {
+        res.add(matrix[rd][startLeft]);
+      }
+      rd++;
+      for(int startUp = rd; startUp <=lu; startUp++) {
+        res.add(matrix[startUp][rl]);
+      }
+      rl--;
+      if(rd <= lu) {
+        for(int startRight = rl; startRight >= lr; startRight--) {
+          res.add(matrix[lu][startRight]);
+        }
+      }
+      lu--;
+      if(lr <= rl) {
+        for(int startDown = lu; startDown >= rd; startDown--) {
+          res.add(matrix[startDown][lr]);
+        }
+      }
+      lr++;
+    }
+    return res;
+  }
+}