Adding 1-Two-Sum.c

Author: FahadulShadhin

c/1-Two-Sum.c

@@ -0,0 +1,43 @@
+/*
+    Time: O(n)
+    Space: O(n)
+*/
+
+typedef struct {
+	int key; // key of hash_table
+	int val;   
+	
+	UT_hash_handle hh; // Makes this structure hashable
+} hash_table;
+
+hash_table *hash = NULL, *elem, *tmp;
+
+int* twoSum(int* nums, int numsSize, int target, int* returnSize){       
+    int* res = calloc((*returnSize = 2), sizeof(int));
+
+	for(int i = 0; i < numsSize; ++i){
+		int k = target - nums[i];
+        
+        HASH_FIND_INT(hash, &k, elem); // Look for the item in hash table
+
+		if (elem) {
+			res[0] = elem->val;
+			res[1] = i;
+			break;
+		} 
+        else {
+			elem = malloc(sizeof(hash_table));
+			elem->key = nums[i]; // array element as key of hash table
+            elem->val = i;       // index of an element as value of hash table
+            
+			HASH_ADD_INT(hash, key, elem); // Add item to hash table
+		}
+	}
+    
+    // Free up the hash table 
+	HASH_ITER(hh, hash, elem, tmp) {
+		HASH_DEL(hash, elem); free(elem); 
+	}
+
+	return res;
+}