diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md
index 5bedd0a0..bc618c15 100644
--- a/problems/0001.两数之和.md
+++ b/problems/0001.两数之和.md
@@ -352,5 +352,86 @@ List<int> twoSum(List<int> nums, int target) {
 }
 ```
 
+C:
+```c
+
+
+/**
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+
+// leetcode 支持 ut_hash 函式庫
+
+ typedef struct {
+     int key;
+     int value;
+     UT_hash_handle hh; // make this structure hashable
+ } map;
+
+map* hashMap = NULL;
+
+ void hashMapAdd(int key, int value){
+     map* s;
+     // key already in the hash?
+     HASH_FIND_INT(hashMap, &key, s);
+     if(s == NULL){
+         s = (map*)malloc(sizeof(map));
+         s -> key = key;
+         HASH_ADD_INT(hashMap, key, s);
+     }
+     s -> value = value;
+ }
+
+map* hashMapFind(int key){
+     map* s;
+     // *s: output pointer
+     HASH_FIND_INT(hashMap, &key, s);   
+     return s;
+ }
+
+ void hashMapCleanup(){
+     map* cur, *tmp;
+     HASH_ITER(hh, hashMap, cur, tmp){
+         HASH_DEL(hashMap, cur);
+         free(cur);
+     }
+ }
+
+ void hashPrint(){
+     map* s;
+     for(s = hashMap; s != NULL; s=(map*)(s -> hh.next)){
+         printf("key %d, value %d\n", s -> key, s -> value);
+     }
+ }
+
+ 
+int* twoSum(int* nums, int numsSize, int target, int* returnSize){
+    int i, *ans;
+    // hash find result
+    map* hashMapRes; 
+    hashMap = NULL;
+    ans = malloc(sizeof(int) * 2);
+
+    for(i = 0; i < numsSize; i++){
+        // key 代表 nums[i] 的值，value 代表所在 index;
+        hashMapAdd(nums[i], i);
+    }
+
+    hashPrint();
+
+    for(i = 0; i < numsSize; i++){
+        hashMapRes = hashMapFind(target - nums[i]);
+        if(hashMapRes && hashMapRes -> value != i){
+            ans[0] = i;
+            ans[1] = hashMapRes -> value ;
+            *returnSize = 2;
+            return ans;
+        }
+    }
+    
+    hashMapCleanup();
+    return NULL;
+}
+```
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