添加 0063.不同路径II.md C语言优化空间版本

Author: KingArthur0205

problems/0063.不同路径II.md

@@ -539,6 +539,39 @@ int uniquePathsWithObstacles(int** obstacleGrid, int obstacleGridSize, int* obst
 }
 ```
 
+空间优化版本:
+```c
+int uniquePathsWithObstacles(int** obstacleGrid, int obstacleGridSize, int* obstacleGridColSize){
+    int m = obstacleGridSize; 
+    int n = obstacleGridColSize[0];
+    int *dp = (int*)malloc(sizeof(int) * n);
+    int i, j;
+
+    // 初始化dp为第一行起始状态。
+    for (j = 0; j < n; ++j) {
+        if (obstacleGrid[0][j] == 1)
+            dp[j] = 0;
+        else if (j == 0)
+            dp[j] = 1;
+        else
+            dp[j] = dp[j - 1];
+    }
+
+    for (i = 1; i < m; ++i) {
+        for (j = 0; j < n; ++j) {
+            if (obstacleGrid[i][j] == 1)
+                dp[j] = 0;
+            // 若j为0，dp[j]表示最左边一列，无需改动
+            // 此处dp[j],dp[j-1]等同于二维dp中的dp[i-1][j]和dp[i][j-1]
+            else if (j != 0)
+                dp[j] += dp[j - 1];
+        }
+    }
+
+    return dp[n - 1];
+}
+```
+
 ### Scala
 
 ```scala