Create 0063-unique-paths-ii.kt

Author: a93a

Diff for: kotlin/0063-unique-paths-ii.kt

@@ -0,0 +1,56 @@
+// If we can't do inplace, space O(N)
+class Solution {
+    fun uniquePathsWithObstacles(grid: Array<IntArray>): Int {
+
+        val m = grid.lastIndex
+        val n = grid[0].lastIndex
+
+        if (grid[m][n] == 1 || grid[0][0] == 1) return 0
+        
+        val dp = IntArray(n+1)
+        dp[n] = 1
+
+        for (i in m downTo 0) {
+            for (j in n downTo 0) {
+                if (grid[i][j] == 1) dp[j] = 0
+                else if (j < n) dp[j] = dp[j] + dp[j + 1]
+                //else dp[j] = dp[j] + 0
+            }
+        }
+    
+        return dp[0]
+    }
+}
+
+// In place O(1)
+class Solution {
+    fun uniquePathsWithObstacles(grid: Array<IntArray>): Int {
+
+        val m = grid.lastIndex
+        val n = grid[0].lastIndex
+
+        if (grid[m][n] == 1 || grid[0][0] == 1) return 0
+        
+        grid[m][n] = 1
+
+        for (i in m-1 downTo 0) {
+            grid[i][n] = if(grid[i][n] == 0 && grid[i + 1][n] == 1) 1 else 0
+        }
+
+        for (i in n-1 downTo 0) {
+            grid[m][i] = if(grid[m][i] == 0 && grid[m][i + 1] == 1) 1 else 0
+        }
+
+        for (i in m-1 downTo 0) {
+            for (j in n-1 downTo 0) {
+                if(grid[i][j] != 1) {
+                    grid[i][j] = grid[i + 1][j] + grid[i][j + 1]
+                } else {
+                    grid[i][j] = 0
+                }   
+            }
+        }
+    
+        return grid[0][0]
+    }
+}