diff --git a/src/167.c b/src/167.c
new file mode 100644
index 0000000..4ff1b21
--- /dev/null
+++ b/src/167.c
@@ -0,0 +1,28 @@
+/**
+ * Return an array of size *returnSize containing the 1-based indices of two numbers 
+ * that add up to the target.
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+#include <stdlib.h>
+int* twoSum(int* numbers, int numbersSize, int target, int* returnSize) {
+    *returnSize = 2;
+    int* output = (int*)malloc(2 * sizeof(int));
+
+    int left =0;
+    int right = numbersSize-1;
+    while(left<right){
+        int sum = numbers[left] + numbers[right];
+        if(sum == target){
+            output[0] = left+1;
+            output[1] = right+1;
+            return output;
+        }
+        else if(sum<target){
+            left++;
+        }
+        else{
+            right--;
+        }
+    }
+    return NULL;
+}
\ No newline at end of file