diff --git a/leetcode/README.md b/leetcode/README.md
index b0a8e0cc..3ac0dccd 100644
--- a/leetcode/README.md
+++ b/leetcode/README.md
@@ -24,6 +24,7 @@ LeetCode
 |109|[Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/) | [C](./src/109.c)|Medium|
 |110|[Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/) | [C](./src/110.c)|Easy|
 |112|[Path Sum](https://leetcode.com/problems/path-sum/) | [C](./src/112.c)|Easy|
+|121|[Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/) | [C](./src/121.c)|Easy|
 |125|[Valid Palindrome](https://leetcode.com/problems/valid-palindrome/) | [C](./src/125.c)|Easy|
 |136|[Single Number](https://leetcode.com/problems/single-number/) | [C](./src/136.c)|Easy|
 |141|[Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/) | [C](./src/141.c)|Easy|
@@ -50,6 +51,7 @@ LeetCode
 |404|[Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/) | [C](./src/404.c)|Easy|
 |442|[Find All Duplicates in an Array](https://leetcode.com/problems/find-all-duplicates-in-an-array/) | [C](./src/442.c)|Medium|
 |461|[Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C](./src/461.c) |Easy|
+|476|[Number Complement](https://leetcode.com/problems/number-complement/) | [C](./src/476.c)|Easy|
 |509|[Fibonacci Number](https://leetcode.com/problems/fibonacci-number/) | [C](./src/509.c)|Easy|
 |520|[Detect Capital](https://leetcode.com/problems/detect-capital/) | [C](./src/520.c)|Easy|
 |561|[Array Partition I](https://leetcode.com/problems/array-partition-i/) | [C](./src/561.c)|Easy|
@@ -71,4 +73,4 @@ LeetCode
 |1089|[Duplicate Zeros](https://leetcode.com/problems/duplicate-zeros/) | [C](./src/1089.c)|Easy|
 |1184|[Distance Between Bus Stops](https://leetcode.com/problems/distance-between-bus-stops/) | [C](./src/1184.c)|Easy|
 |1189|[Maximum Number of Balloons](https://leetcode.com/problems/maximum-number-of-balloons/) | [C](./src/1189.c)|Easy|
-|1207|[Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/) | [C](./src/1207.c)|Easy|
+|1207|[Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/) | [C](./src/1207.c)|Easy|
\ No newline at end of file
diff --git a/leetcode/src/121.c b/leetcode/src/121.c
new file mode 100644
index 00000000..2741ce99
--- /dev/null
+++ b/leetcode/src/121.c
@@ -0,0 +1,17 @@
+int maxcmp(int a, int b) {
+	return (a >= b)? a : b;
+}
+
+/* max subarray problem by using Kadane's Algorithm
+ */
+int maxProfit(int* prices, int pricesSize){
+	/* maxCur: current maximum 
+	 * maxSoFar: found maximum for subarray so far
+	 */
+	int maxCur = 0, maxSoFar = 0;
+	for(int i = 1; i < pricesSize; i++) {
+		maxCur = maxcmp(0, maxCur + prices[i] - prices[i - 1]);
+		maxSoFar = maxcmp(maxSoFar, maxCur);
+	}
+	return maxSoFar;
+}
diff --git a/leetcode/src/35.c b/leetcode/src/35.c
index 6db6431b..31c507c2 100644
--- a/leetcode/src/35.c
+++ b/leetcode/src/35.c
@@ -11,3 +11,15 @@ int searchInsert(int* nums, int numsSize, int target){
     }
     return low;
 }
+
+/* Recursive version */
+int searchInsert(int* nums, int numsSize, int target){
+    int idx = numsSize - 1;
+    if(numsSize>0){
+        if (target > nums[idx]){
+            return numsSize;
+        }
+        return searchInsert(nums, numsSize - 1, target);
+    }
+    return 0;
+}
diff --git a/leetcode/src/476.c b/leetcode/src/476.c
new file mode 100644
index 00000000..f6ee952f
--- /dev/null
+++ b/leetcode/src/476.c
@@ -0,0 +1,15 @@
+int findComplement(int num) {
+    int TotalBits = 0;
+    int temp = num;
+    while(temp) {               //To find position of MSB in given num. Since num is represented as a standard size in memory, we cannot rely on size
+                                //for that information.
+        TotalBits++;            //increment TotalBits till temp becomes 0
+        temp >>= 1;             //shift temp right by 1 bit every iteration; temp loses 1 bit to underflow every iteration till it becomes 0
+    }
+    int i, flipNumber = 1;      //Eg: 1's complement of 101(binary) can be found as 101^111 (XOR with 111 flips all bits that are 1 to 0 and flips 0 to 1)
+    for(i = 1; i < TotalBits; i++) {
+        flipNumber += UINT32_C(1) << i; //Note the use of unsigned int to facilitate left shift more than 31 times, if needed
+    }
+    num = num^flipNumber;
+    return num;
+}
\ No newline at end of file