Add python codes and for the chapter of

computational complexity.
Update Java codes.
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codes/go/chapter_computational_complexity/leetcode_two_sum.go

@@ -7,6 +7,7 @@ package chapter_computational_complexity
 // twoSumBruteForce
 func twoSumBruteForce(nums []int, target int) []int {
 	size := len(nums)
+	// 两层循环，时间复杂度 O(n^2)
 	for i := 0; i < size-1; i++ {
 		for j := i + 1; i < size; j++ {
 			if nums[i]+nums[j] == target {
@@ -19,7 +20,9 @@ func twoSumBruteForce(nums []int, target int) []int {
 
 // twoSumHashTable
 func twoSumHashTable(nums []int, target int) []int {
+	// 辅助哈希表，空间复杂度 O(n)
 	hashTable := map[int]int{}
+	// 单层循环，时间复杂度 O(n)
 	for idx, val := range nums {
 		if preIdx, ok := hashTable[target-val]; ok {
 			return []int{preIdx, idx}