Add C++ solution for leetcode 335.

Author: yanglr

cpp-leetcode/leetcode335-self-crossing_case_by_classification.cpp

@@ -0,0 +1,36 @@
+#include<vector>
+#include<algorithm>
+#include<iostream>
+using namespace std;
+
+class Solution {
+public:
+    bool isSelfCrossing(vector<int>& A) {
+        const int N = A.size();
+        if (N <= 3) return false;
+        for (int i = 3; i < N; i++)
+        {
+            // case1: 4步之内有交点
+            if (A[i-1] <= A[i-3] && A[i] >= A[i-2])
+                return true;
+            // case 2: 5步之内有交点
+            if (i >= 4 && A[i-3] == A[i-1] && A[i] + A[i-4] >= A[i-2])
+                return true;
+            // case 3: 6步之内有交点
+            if (i >= 5 && A[i-3] >= A[i-1] && A[i-1] + A[i-5] >= A[i-3] && A[i-2] >= A[i-4] && A[i-4] + A[i] >= A[i-2])
+                return true;            
+        }
+        return false;
+    }
+};
+
+// Test
+int main()
+{
+    Solution sol;
+    vector<int> nums = {2,1,1,2};
+    auto res = sol.isSelfCrossing(nums);
+    cout << (res ? "True" : "False") << endl;
+
+    return 0;
+}