[20251121] PGM / Lv2 / 삼각 달팽이 / 이강현

lkhyun/202511/21 PGM Lv2 삼각 달팽이.md

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+```java
+class Solution {
+    public int[] solution(int n) {
+        int[][] arr = new int[n][];
+        for(int i = 0; i<n ;i++){
+            arr[i] = new int[i+1];
+        }
+        int row = 0, col = 0;
+        int num = 1;
+        int total = n*(n+1)/2;
+        int state = 0; // 0:down, 1:right, 2:up
+        while(num <= total){
+            arr[row][col] = num++;
+            if(state == 0){
+                if(row+1 == n || arr[row+1][col] != 0){
+                    state = 1;
+                    col++;    
+                }else{
+                    row++;   
+                }
+            }else if(state == 1){
+                if(col == row || arr[row][col+1] != 0){
+                    state = 2;
+                    row--;
+                    col--;
+                }else{
+                    col++;
+                }
+            }else if(state == 2){
+                if(arr[row-1][col-1] != 0){
+                    state = 0;
+                    row++;
+                }else{
+                    row--;
+                    col--;
+                }
+            }
+        }
+
+        int[] answer = new int[total];
+        int idx = 0;
+        for(int i = 0; i<n; i++){
+            for(int j = 0; j<arr[i].length; j++){
+                answer[idx++] = arr[i][j];
+            }
+        }
+        return answer;
+    }
+}
+```