Implement islandPerimeter function to calculate perimeter

Author: jyoung2419

leetcode3/정진영/463. Island Perimeter

@@ -0,0 +1,27 @@
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var islandPerimeter = function(grid) {
+    let count = 0;
+
+    for (let i = 0; i<grid.length; i++){
+        for (let j = 0; j<grid[0].length; j++){
+            // land 일 때
+            if (grid[i][j] == 1){
+                count += 4;
+
+                if (j>0 && grid[i][j-1] == 1){
+                    count -= 1;
+                } if (i>0 && grid[i-1][j] == 1){
+                    count -= 1;
+                } if (j<grid[0].length-1 && grid[i][j+1] == 1){
+                    count -= 1;
+                } if (i<grid.length-1 && grid[i+1][j] == 1){
+                    count -= 1;
+                }
+            }
+        }
+    }
+    return count;
+};