修正0001.两数之和dart

- 儘量給定類型
- 使用HashMap取代不適合的List

problems/0001.两数之和.md

@@ -402,16 +402,18 @@ public class Solution {
 ### Dart:
 
 ```dart
-List<int> twoSum(List<int> nums, int target) {  
-    var tmp = [];
-    for (var i = 0; i < nums.length; i++) {
-        var rest = target - nums[i];
-        if(tmp.contains(rest)){
-            return [tmp.indexOf(rest), i];
-        }
-        tmp.add(nums[i]);
+import 'dart:collection';
+
+List<int> twoSum(List<int> nums, int target) {
+  HashMap<int, int> hashMap = HashMap();
+  for (int i = 0; i < nums.length; i++) {
+    int rest = target - nums[i];
+    if (hashMap.containsKey(rest)) {
+      return [hashMap[rest]!, i];
     }
-    return [0 , 0];
+    hashMap.addEntries({nums[i]: i}.entries);
+  }
+  return [];
 }
 ```