From f4328e7dc99dc5f1ac56300fe5d42c648c218be4 Mon Sep 17 00:00:00 2001
From: lxzan <lxzan520@gmail.com>
Date: Thu, 28 Dec 2023 09:28:15 +0800
Subject: [PATCH] add methods for vector

---
 algorithm/{helper.go => algorithm.go}           |  8 ++++----
 algorithm/{helper_test.go => algorithm_test.go} |  4 ++--
 vector/vector.go                                | 16 ++++++++++++++++
 vector/vector_test.go                           |  6 ++++++
 4 files changed, 28 insertions(+), 6 deletions(-)
 rename algorithm/{helper.go => algorithm.go} (93%)
 rename algorithm/{helper_test.go => algorithm_test.go} (96%)

diff --git a/algorithm/helper.go b/algorithm/algorithm.go
similarity index 93%
rename from algorithm/helper.go
rename to algorithm/algorithm.go
index 1d6db90..0615065 100644
--- a/algorithm/helper.go
+++ b/algorithm/algorithm.go
@@ -76,14 +76,14 @@ func UniqueBy[T any, K cmp.Ordered, A ~[]T](arr A, getKey func(item T) K) A {
 // Sum 求和
 func Sum[T cmp.Number](arr []T) T {
 	var sum T
-	return Reduce(arr, sum, func(s T, item T) T { return s + item })
+	return Reduce(arr, sum, func(s T, i int, v T) T { return s + v })
 }
 
 // Reduce 对数组中的每个元素按序执行一个提供的 reducer 函数，每一次运行 reducer 会将先前元素的计算结果作为参数传入，
 // 最后将其结果汇总为单个返回值。
-func Reduce[T any, S any](arr []T, initialValue S, reducer func(s S, item T) S) S {
-	for _, item := range arr {
-		initialValue = reducer(initialValue, item)
+func Reduce[T any, S any](arr []T, initialValue S, reducer func(s S, i int, v T) S) S {
+	for index, value := range arr {
+		initialValue = reducer(initialValue, index, value)
 	}
 	return initialValue
 }
diff --git a/algorithm/helper_test.go b/algorithm/algorithm_test.go
similarity index 96%
rename from algorithm/helper_test.go
rename to algorithm/algorithm_test.go
index 2af0eb0..117138e 100644
--- a/algorithm/helper_test.go
+++ b/algorithm/algorithm_test.go
@@ -187,7 +187,7 @@ func TestIsZero(t *testing.T) {
 func TestReduce(t *testing.T) {
 	t.Run("", func(t *testing.T) {
 		var arr = []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
-		var sum = Reduce(arr, 0, func(summarize int, item int) int {
+		var sum = Reduce(arr, 0, func(summarize int, i int, item int) int {
 			return summarize + item
 		})
 		assert.Equal(t, sum, 55)
@@ -196,7 +196,7 @@ func TestReduce(t *testing.T) {
 	t.Run("", func(t *testing.T) {
 		var arr = []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
 		var m = hashmap.New[int, struct{}](10)
-		Reduce(arr, m, func(s hashmap.HashMap[int, struct{}], item int) hashmap.HashMap[int, struct{}] {
+		Reduce(arr, m, func(s hashmap.HashMap[int, struct{}], i int, item int) hashmap.HashMap[int, struct{}] {
 			s.Set(item, struct{}{})
 			return s
 		})
diff --git a/vector/vector.go b/vector/vector.go
index 91fe238..8958daa 100644
--- a/vector/vector.go
+++ b/vector/vector.go
@@ -27,11 +27,27 @@ func (c *Vector[K, V]) Len() int {
 	return len(*c)
 }
 
+func (c *Vector[K, V]) Cap() int {
+	return cap(*c)
+}
+
 // Get 根据下标取值
 func (c *Vector[K, V]) Get(index int) V {
 	return (*c)[index]
 }
 
+// Front 获取头部元素
+// 注意: 未作越界检查
+func (c *Vector[K, V]) Front() V {
+	return c.Get(0)
+}
+
+// Back 获取尾部元素
+// 注意: 未作越界检查
+func (c *Vector[K, V]) Back() V {
+	return c.Get(c.Len() - 1)
+}
+
 // Delete 根据下标删除某个元素
 // 性能不好, 少用
 func (c *Vector[K, V]) Delete(index int) {
diff --git a/vector/vector_test.go b/vector/vector_test.go
index 846032d..a903717 100644
--- a/vector/vector_test.go
+++ b/vector/vector_test.go
@@ -254,3 +254,9 @@ func TestVector_Delete(t *testing.T) {
 		assert.True(t, utils.IsSameSlice(v.Elem(), []Int{1, 5, 7}))
 	})
 }
+
+func TestVector_Get(t *testing.T) {
+	var v = NewFromInts(1, 3, 5)
+	assert.Equal(t, v.Front(), Int(1))
+	assert.Equal(t, v.Back(), Int(5))
+}