add Space Complexity( O(n) ) & simpler solution

Author: zouwx2cs

solution/0120.Triangle/Solution2.cpp

@@ -0,0 +1,12 @@
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        vector<int> dp(triangle.back()) ;
+        
+        for (int i = triangle.size()-2; i >= 0; --i)
+            for (int j = 0; j <= i; ++j)
+                dp[j] = triangle[i][j] + min(dp[j], dp[j+1]) ;
+        
+        return dp[0] ;
+    }
+};