Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9, Because nums[0] + nums[1] = 2 + 7 = 9, return [0, 1].
解答：
public int[] twoSum(int[] nums, int target) {
int length = nums.length;
for(int i = 0;i<length-1;i++){
for(int j=i+1;j<length;j++){
if(nums[i]+nums[j]==target){
return new int[]{i,j};
}
}
}
return null;
}