添加 problem 1

Algorithms/1.Two Sum/1. Add Two Numbers.go

@@ -0,0 +1,43 @@
+package leetcode
+
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+	if l1 == nil || l2 == nil {
+		return nil
+	}
+	head := &ListNode{Val: 0, Next: nil}
+	current := head
+	carry := 0
+	for l1 != nil || l2 != nil {
+		var x, y int
+		if l1 == nil {
+			x = 0
+		} else {
+			x = l1.Val
+		}
+		if l2 == nil {
+			y = 0
+		} else {
+			y = l2.Val
+		}
+		current.Next = &ListNode{Val: (x + y + carry) % 10, Next: nil}
+		current = current.Next
+		carry = (x + y + carry) / 10
+		if l1 != nil {
+			l1 = l1.Next
+		}
+		if l2 != nil {
+			l2 = l2.Next
+		}
+	}
+	if carry > 0 {
+		current.Next = &ListNode{Val: carry % 10, Next: nil}
+	}
+	return head.Next
+}

Algorithms/1.Two Sum/1. Add Two Numbers_test.go

@@ -0,0 +1,79 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question2 struct {
+	para2
+	ans2
+}
+
+// para 是参数
+// one 代表第一个参数
+type para2 struct {
+	one     []int
+	another []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans2 struct {
+	one []int
+}
+
+func Test_Problem2(t *testing.T) {
+
+	qs := []question2{
+
+		question2{
+			para2{[]int{}, []int{}},
+			ans2{[]int{}},
+		},
+
+		question2{
+			para2{[]int{1}, []int{1}},
+			ans2{[]int{2}},
+		},
+
+		question2{
+			para2{[]int{1, 2, 3, 4}, []int{1, 2, 3, 4}},
+			ans2{[]int{2, 4, 6, 8}},
+		},
+
+		question2{
+			para2{[]int{1, 2, 3, 4, 5}, []int{1, 2, 3, 4, 5}},
+			ans2{[]int{2, 4, 6, 8, 0, 1}},
+		},
+
+		question2{
+			para2{[]int{1}, []int{9, 9, 9, 9, 9}},
+			ans2{[]int{0, 0, 0, 0, 0, 1}},
+		},
+
+		question2{
+			para2{[]int{9, 9, 9, 9, 9}, []int{1}},
+			ans2{[]int{0, 0, 0, 0, 0, 1}},
+		},
+
+		question2{
+			para2{[]int{2, 4, 3}, []int{5, 6, 4}},
+			ans2{[]int{7, 0, 8}},
+		},
+
+		question2{
+			para2{[]int{1, 8, 3}, []int{7, 1}},
+			ans2{[]int{8, 9, 3}},
+		},
+		// 如需多个测试，可以复制上方元素。
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 2------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans2, q.para2
+		fmt.Printf("【input】:%v       【output】:%v\n", p, L2s(addTwoNumbers(S2l(p.one), S2l(p.another))))
+	}
+	fmt.Printf("\n\n\n")
+}

Algorithms/1.Two Sum/README.md

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+# [1. Two Sum](https://leetcode.com/problems/two-sum/)
+
+## 题目
+
+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].
+```
+
+
+
+## 题目大意
+
+在数组中找到 2 个数之和等于给定值的数字，结果返回 2 个数字在数组中的下标。
+
+这道题最优的做法时间复杂度是 O(n)。
+
+顺序扫描数组，对每一个元素，在 map 中找能组合给定值的另一半数字，如果找到了，直接返回 2 个数字的下标即可。如果找不到，就把这个数字存入 map 中，等待扫到“另一半”数字的时候，再取出来返回结果。