update the leetcode problem

lectures/03_classes_I/README.md

@@ -144,6 +144,6 @@ bool earlier_date (const Date& a, const Date& b) {
 
 ## 3.11 Exercises
 
-- [Leetcode problem 8: String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)
+- [Leetcode problem 1051: Height Checker](https://leetcode.com/problems/height-checker/) [Solution](../../leetcode/p1051_heightchecker.cpp)
 - [Leetcode problem 211: Design Add and Search Words Data Structure](https://leetcode.com/problems/design-add-and-search-words-data-structure/)
 - [Leetcode problem 1662: Check If Two String Arrays are Equivalent](https://leetcode.com/problems/check-if-two-string-arrays-are-equivalent/)

leetcode/p1051_heightchecker.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    int heightChecker(vector<int>& heights) {
+        int count = 0;
+        int size = heights.size();
+        vector<int> expected(heights);
+        sort(expected.begin(),expected.end());
+        for(int i=0;i<size;i++){
+            if(heights[i]!=expected[i]){
+                count++;
+            }
+        }
+        return count;
+    }
+};