diff --git a/heap/heap.go b/heap/heap.go
index 35c27ff..feab4c6 100644
--- a/heap/heap.go
+++ b/heap/heap.go
@@ -2,15 +2,18 @@ package heap
 
 import (
 	"474420502.top/eson/structure/compare"
+	"474420502.top/eson/structure/sparse_array/array3"
 )
 
 type Heap struct {
 	size     int
 	cap      int
-	elements []interface{}
+	elements *array3.Array3
 	Compare  compare.Compare
 }
 
 func New(Compare compare.Compare) *Heap {
-	return &Heap{Compare: Compare, cap: 8}
+	h := &Heap{Compare: Compare, cap: 8}
+	h.elements = array3.NewWithCap(4, 4, 4)
+	return h
 }
diff --git a/sparse_array/array2/array2.go b/sparse_array/array2/array2.go
index 273ae4f..9611e90 100644
--- a/sparse_array/array2/array2.go
+++ b/sparse_array/array2/array2.go
@@ -5,6 +5,8 @@ type Array2 struct {
 	ysize int
 	xsize int
 	data  [][]interface{}
+
+	cap int
 }
 
 func New() *Array2 {
@@ -15,6 +17,8 @@ func NewWithCap(ysize, xsize int) *Array2 {
 	arr := &Array2{ysize: ysize, xsize: xsize}
 	arr.sizes = make([]int, arr.ysize, arr.ysize)
 	arr.data = make([][]interface{}, arr.ysize, arr.ysize)
+
+	arr.cap = arr.ysize * arr.xsize
 	return arr
 }
 
@@ -58,6 +62,10 @@ func (arr *Array2) Values() []interface{} {
 	return result
 }
 
+func (arr *Array2) Cap() int {
+	return arr.cap
+}
+
 func (arr *Array2) Grow(size int) {
 	arr.ysize += size
 	temp := make([][]interface{}, arr.ysize, arr.ysize)
@@ -67,6 +75,8 @@ func (arr *Array2) Grow(size int) {
 	tempsizes := make([]int, arr.ysize, arr.ysize)
 	copy(tempsizes, arr.sizes)
 	arr.sizes = tempsizes
+
+	arr.cap = arr.ysize * arr.xsize
 }
 
 func (arr *Array2) Set(idx int, value interface{}) {
diff --git a/sparse_array/array3/array3.go b/sparse_array/array3/array3.go
index b87a50a..d232c55 100644
--- a/sparse_array/array3/array3.go
+++ b/sparse_array/array3/array3.go
@@ -8,6 +8,8 @@ type Array3 struct {
 	ysize     int
 	xsize     int
 	data      [][][]interface{}
+
+	cap int
 }
 
 func New() *Array3 {
@@ -26,6 +28,8 @@ func NewWithCap(zsize, ysize, xsize int) *Array3 {
 
 	arr.xyproduct = arr.ysize * arr.xsize
 	arr.data = make([][][]interface{}, arr.zsize, arr.zsize)
+
+	arr.cap = arr.zsize * arr.xyproduct
 	return arr
 }
 
@@ -87,8 +91,12 @@ func (arr *Array3) Values() []interface{} {
 	return result
 }
 
+func (arr *Array3) Cap() int {
+	return arr.cap
+}
+
 func (arr *Array3) Grow(size int) {
-	arr.ysize += size
+	arr.zsize += size
 	temp := make([][][]interface{}, arr.zsize, arr.zsize)
 	copy(temp, arr.data)
 	arr.data = temp
@@ -100,6 +108,8 @@ func (arr *Array3) Grow(size int) {
 	tempxsizes := make([][]int, arr.ysize, arr.ysize)
 	copy(tempxsizes, arr.xsizes)
 	arr.xsizes = tempxsizes
+
+	arr.cap = arr.zsize * arr.xyproduct
 }
 
 func (arr *Array3) Set(idx int, value interface{}) {
diff --git a/sparse_array/arrayn/arrayn.go b/sparse_array/arrayn/arrayn.go
index 54252d3..f29317f 100644
--- a/sparse_array/arrayn/arrayn.go
+++ b/sparse_array/arrayn/arrayn.go
@@ -23,6 +23,8 @@ type ArrayN struct {
 
 	dimN int
 	data *Node // []*Node
+
+	cap int
 }
 
 func New() *ArrayN {
@@ -40,6 +42,10 @@ func NewWithCap(dims ...int) *ArrayN {
 		arr.product[i] = pvalue
 	}
 	// arr.data = make([]*Node, arr.dims[0], arr.dims[0])
+	arr.cap = 1
+	for _, d := range arr.dims {
+		arr.cap *= d
+	}
 	return arr
 }
 
@@ -107,6 +113,10 @@ func (arr *ArrayN) set(curDim int, curidx int, pdata **Node, parent *Node) (*Nod
 	return arr.set(curDim-1, nidx, &cur.data.([]*Node)[dimindex], cur)
 }
 
+func (arr *ArrayN) Cap() int {
+	return arr.cap
+}
+
 func (arr *ArrayN) Grow(size int) {
 	arr.dims[0] += size
 
@@ -121,6 +131,11 @@ func (arr *ArrayN) Grow(size int) {
 	newData := make([]*Node, arr.dims[0], arr.dims[0])
 	copy(newData, tempdata)
 	arr.data.data = newData
+
+	arr.cap = 1
+	for _, d := range arr.dims {
+		arr.cap *= d
+	}
 }
 
 func (arr *ArrayN) Set(idx int, value interface{}) {