## TwoSum Solution in Dart

## First Solution

```
class Solution {
// BRUTE FORCE SOLUTION - SIMPLE
// Runtime of this solution is 362ms
List<int> twoSum(List<int> numbers, int target) {
// it indicates the whole length of the list
int n = numbers.length;
// for loop for tracking the first value
for (var i = 0; i < n - 1; i++) {
// for loop for keep tracking the second value inside the list
for (var j = i + 1; j < n; j++) {
// condition that dictates the first of any value inside the list and second inside the
// list should be equal to target
if (numbers[i] + numbers[j] == target) {
// then we return the list of first value and second
return [i, j];
}
}
}
return [];
}
}
```

## Second Solution

Using map to keeping an eye on the values of the list

Sadly in LeetCode the HashMap is not working but it perfectly working outside the leetcode.

So I use Map instead of Hash Map

```
class Solution {
// In LeetCode the HashMap is not fully implemented
// Runtime 503
List<int> twoSum(List<int> nums, int target) {
// Map to keep an eye on the close range, simply correlation
final Map<int, int> correspondence = Map<int, int>();
// loop through the entire list values
for (var i = 0; i < nums.length; i++) {
// saving value inside a variable
final int value = nums[i];
// we are getting key in a very tricky way like target value which
// we will enter and than we will subtract the single value
//that we got from looping from the list.
//
final int key = target - value;
if (correspondence.containsKey(key)) {
// than we will return if int of the map and the second int
// which shows the position in a list which two value will result the target value
return [correspondence[key]!, i];
}
// here we defining that our key will i the digit inside of our list
// if we don't do this than it will return the value of the list which is inside the list
correspondence[value] = i;
// Remember = correspondence[key] is Our key , correspondence[value] is Our Value
}
return [];
}
}
```

## Third Solution

This work like a charm in terminal because dart does not keep track of the index number in list. I have created a extension to work with the list but for leetCode let's not make complicated

```
class Solution
// Working perfect in Terminal
// but runtime error inclusive range error
List<int> twoSum(List<int> nums, int target) {
List<int> result = <int>[];
for (var i = 0; i < nums.length; i++) {
int complement = target - nums[i];
var index = nums.indexOf(complement, i + 1);
if (nums[index] + nums[i] == target) {
return result = [i, index];
}
break;
}
return result;
}
}
```

```
// to keep track on the index
extension SubScript<T> on List<T>{
T? operator [](int index)=> length > index ? elementAt(index) : null;
}
```

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