Lintcode/src/chapter4_DynamicProgrammingI/UniquePathsII.java

fishercoder1534 · fishercoder1534 · commit c35778cca64e · 2016-09-10T15:09:44.000-07:00
diff --git a/Lintcode/src/chapter4_DynamicProgrammingI/UniquePathsII.java b/Lintcode/src/chapter4_DynamicProgrammingI/UniquePathsII.java
@@ -0,0 +1,53 @@
+package chapter4_DynamicProgrammingI;
+/**Follow up for "Unique Paths":
+
+Now consider if some obstacles are added to the grids. How many unique paths would there be?
+
+An obstacle and empty space is marked as 1 and 0 respectively in the grid.
+
+ Notice
+
+m and n will be at most 100.*/
+public class UniquePathsII {
+
+    /**
+     * @param obstacleGrid: A list of lists of integers
+     * @return: An integer
+     */
+    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
+        // write your code here
+        if(obstacleGrid == null || obstacleGrid.length == 0) return 0;
+        int m = obstacleGrid.length, n = obstacleGrid[0].length;
+        int[][] ways = new int[m][n];
+        
+        for(int i = 0; i < m; i++){
+            if(obstacleGrid[i][0] == 0) ways[i][0] = 1;
+            else {
+                while(i < m){
+                    ways[i][0] = 0;
+                    i++;
+                }
+            }
+        }
+        
+        for(int j = 0; j < n; j++){
+            if(obstacleGrid[0][j] == 0) ways[0][j] = 1;
+            else {
+                while(j < n){
+                    ways[0][j] = 0;
+                    j++;
+                }
+            }
+        }
+        
+        for(int i = 1; i < m; i++){
+            for(int j = 1; j < n; j++){
+                if(obstacleGrid[i][j] == 1) ways[i][j] = 0;
+                else ways[i][j] = ways[i-1][j] + ways[i][j-1];
+            }
+        }
+        
+        return ways[m-1][n-1];
+    }
+
+}
