diff --git a/01-knapsack.cpp b/01-knapsack.cpp
new file mode 100644
index 0000000..ae3dcde
--- /dev/null
+++ b/01-knapsack.cpp
@@ -0,0 +1,57 @@
+#include <iostream>
+#include <algorithm>
+using namespace std;
+
+const int N = 5;			// number of items
+const int C = 10;			// capacity of bag
+int w[N + 1] = {0, 2, 2, 6, 5, 4};
+int v[N + 1] = {0, 6, 3, 5, 4, 6};
+int f[N + 1][C + 1] = {{0}};
+int ff[N + 1] = {0};
+
+/*
+recurrence equation:
+f(i,j) = max{f(i - 1,j - w[i]) + v[i](j>=w[i]), f(i - 1,j)} 
+*/
+int Knapsack()
+{
+	for(int i = 1; i <= N; i++)
+	{
+		for(int j = 1; j <= C; j++)
+		{
+			if(j >= w[i])
+				f[i][j] = max(f[i-1][j],f[i-1][j-w[i]] + v[i]);
+			else
+				f[i][j] = f[i-1][j];
+		}
+	}
+	return f[N][C];
+}
+
+/*
+space optimization
+recurrence equation:
+f(j) = max{f(j - w[i]) + v[i](j>=w[i]), f(j)} 
+*/
+
+int Knapsack_SpaceOpt()
+{
+	for(int i = 1; i <= N; i++)
+	{
+		for(int j = C; j >= w[i]; j--)		//set low bound to be w[i]
+		{
+			if(j >= w[i])
+				ff[j] = max(ff[j], ff[j - w[i] + v[i]]);
+			else
+				ff[j] = ff[j];
+		}
+	}
+	return f[N][C];
+}
+
+int main()
+{
+	cout << Knapsack() << endl;
+	cout << Knapsack_SpaceOpt() << endl;
+	return 0;
+}
\ No newline at end of file
diff --git a/btsearch.cpp b/btsearch.cpp
deleted file mode 100644
index f908d6f..0000000
--- a/btsearch.cpp
+++ /dev/null
@@ -1,76 +0,0 @@
-#include <iostream>
-#include <Stack>
-#include <Queue>
-using namespace std;
-
-int index = 0;
-
-typedef struct Node
-{
-	char data;
-	struct Node *lchild;
-	struct Node *rchild;
-}* Tree;
-
-void treeConstructor(Tree &node, char data[])
-{
-	char e = data[index++];
-	if(e == '#')
-		node = nullptr;
-	else
-	{
-		node = new Node;
-		node->data = e;
-		treeConstructor(node->lchild, data);
-		treeConstructor(node->rchild, data);
-	}
-}
-
-void DFS(Tree root)
-{
-	stack<Node *> nodeStack;
-	nodeStack.push(root);
-	Node *node;
-	while(!nodeStack.empty())
-	{
-		node = nodeStack.top();
-		cout << node->data;
-		nodeStack.pop();
-		if(node->rchild)
-			nodeStack.push(node->rchild);
-		if(node->lchild)
-			nodeStack.push(node->lchild);
-	}
-}
-
-void BFS(Tree root)
-{
-	queue<Node *>nodeQueue;
-	nodeQueue.push(root);
-	Node *node;
-	while(!nodeQueue.empty())
-	{
-		node = nodeQueue.front();
-		cout << node->data;
-		nodeQueue.pop();
-		if(node->lchild)
-			nodeQueue.push(node->lchild);
-		if(node->rchild)
-			nodeQueue.push(node->rchild);
-	}
-}
-
-int main()
-{
-	char data[16] = {'A', 'B', 'D', '#', '#', 'E', '#', '#', 'C', 'F', '#', '#', 'G', '#', '#', '\0'};
-	Tree root;
-	treeConstructor(root, data);
-	cout << "DFS: ";
-	DFS(root);
-	cout << endl;
-	cout << "DFS: ";
-	BFS(root);
-	cout << endl;
-
-	return 0;
-}
diff --git a/eight_queens.cpp b/eight_queens.cpp
new file mode 100644
index 0000000..97aac26
--- /dev/null
+++ b/eight_queens.cpp
@@ -0,0 +1,57 @@
+#include <iostream>
+using namespace std;
+
+int a[8],n = 8,i,j,t=1;
+
+//参考:http://blog.csdn.net/bone_ace/article/details/41419695
+
+//Check函数检验第n行的皇后是否和之前的皇后有冲突，没有冲突返回1
+
+/*约束条件：
+1.不在同一列：a[n] != a[i]
+2.不在同一行：因为现在是每一行求一个皇后的位置，所以同一行不会有冲突，不需要考虑。
+3.不在同一对左角线：a[n]-a[i] != n-i
+4.不在同一右对角线：a[n]-a[i] != -(n-i)
+条件3和4可以合成：abs(a[n]-a[i]) != abs(n-i)
+*/
+int Check(int a[],int n)
+{
+	for(int i=1;i<n;i++)
+	{
+		if(abs(a[i]-a[n])==abs(i-n) || a[i]==a[n])
+			return 0;
+	}
+	return 1;
+}
+
+//利用递归实现深度优先搜索和回溯
+void Try(int i)
+{
+	int j,k;
+	for(j=1;j<=n;j++)
+	{
+		a[i]=j;
+		if(Check(a,i))	//如果第j列不会与之前的皇后冲突
+		{
+			//如果i<n，即还没有找到八个皇后，继续递归
+			if(i<n)
+				Try(i+1);
+			//如果找到了一组解就输出
+			else
+			{
+				printf("第%d种解法：\n",t++);
+				for(k=1;k<=n;k++)
+					printf("第%d个皇后：%d\n",j,a[k]);
+				printf("\n\n");
+			}
+		}
+	}
+}
+
+int main()
+{
+	cout << "n=" << n << endl;
+	Try(1);
+
+	return 0;
+}
\ No newline at end of file
diff --git a/fractional_knapsack.cpp b/fractional_knapsack.cpp
new file mode 100644
index 0000000..123a9cf
--- /dev/null
+++ b/fractional_knapsack.cpp
@@ -0,0 +1,64 @@
+#include <iostream>
+#include <algorithm>
+using namespace std;
+
+const int N = 5;			// number of items
+const int C = 10;			// capacity of bag
+
+struct Item
+{
+	float weight;
+	float value;
+	float ratio;
+};
+
+bool compare(Item a, Item b)
+{
+	return a.ratio > b.ratio;
+}
+
+float Fractional_Knapsack(Item (&item)[N])	// greedy algorithm
+{
+	float value = 0;
+	float capacity = C;
+	float tmp[N];
+
+	sort(item, item + N, compare);
+
+	for(int i = 0; i < N; i++)
+	{
+		if(item[i].weight < capacity)
+		{
+			value += item[i].value;
+			capacity -= item[i].weight;
+			tmp[i] = 1;
+		}
+		else
+		{
+			tmp[i] = capacity/item[i].weight;
+			value += item[i].value * tmp[i];
+			capacity = 0;
+		}
+	}
+
+	return value;
+}
+
+int main()
+{
+	float w[N] = {2.0, 2.0, 6.0, 5.0, 4.0};
+	float v[N] = {6.0, 3.0, 5.0, 4.0, 6.0};
+	Item item[N];
+	
+	for(int i = 0; i < N; i++)
+	{
+		item[i].weight = w[i];
+		item[i].value = v[i];
+		item[i].ratio = v[i]/w[i];
+		cout << item[i].ratio<< " ";
+	}
+	cout << endl;
+	cout << Fractional_Knapsack(item) << endl;
+
+	return 0;
+}
\ No newline at end of file
diff --git a/graphSearch.cpp b/graphSearch.cpp
deleted file mode 100644
index ff144a0..0000000
--- a/graphSearch.cpp
+++ /dev/null
@@ -1,99 +0,0 @@
-#include <iostream>
-#include <Stack>
-#include <Queue>
-using namespace std;
-
-const int vnum = 5;
-int visited[vnum];
-
-struct Graph
-{
-	int vertex[vnum];
-	int arc[vnum][vnum];
-};
-
-void CreatGraph(Graph &G, int data[], int maxtrix[][vnum])
-{
-	for(int i = 0; i < vnum; i++)
-		G.vertex[i] = data[i];
-	for(int i = 0; i < vnum; i++)
-		for(int j = 0; j < vnum; j++)
-			G.arc[i][j] = maxtrix[i][j];
-}
-
-void DFS(Graph *G, int v)
-{
-	if(!visited[v])
-	{
-		cout << G->vertex[v];
-		visited[v] = 1;
-	}
-	for(int i = 0; i < vnum; i++)
-		if(G->arc[v][i] && visited[i] != 1)
-			DFS(G, i);
-}
-
-void BFS(Graph *G, int v)
-{
-	int f;
-	queue<int> q;
-	if(!visited[v])
-	{
-		cout << G->vertex[v];
-		visited[v] = 1;
-		q.push(v);
-	}
-	while(!q.empty())
-	{
-		f = q.front();
-		q.pop();
-		for(int i = 0; i < vnum; i++)
-			if(G->arc[f][i] && visited[i] != 1)
-			{
-				cout << G->vertex[i];
-				visited[i] = 1;
-				q.push(i);
-			}
-	}
-}
-
-int main()
-{
-	Graph *G = new Graph;
-
-	int data[vnum] = {1, 2, 3, 4, 5};
-	int arcMatrix[vnum][vnum] = 
-	{
-		{0, 1, 1, 0, 0},
-		{1, 0, 0, 1, 0},
-		{1, 0, 0, 1, 1},
-		{0, 1, 1, 0, 1},
-		{0, 0, 1, 1, 0},
-	};
-
-	CreatGraph(*G, data, arcMatrix);
-	cout << "vertex: ";
-	for(int i = 0; i < vnum; i++)
-		cout << G->vertex[i];
-	cout << endl << "arc: " << endl;
-	for(int i = 0; i < vnum; i++)
-	{
-		cout << "  ";
-		for(int j = 0; j < vnum; j++)
-			cout << G->arc[i][j];
-		cout << endl;
-	}
-	cout << endl;
-
-	cout << "DFS: " << endl;
-	DFS(G, 0);
-	cout << endl;
-
-	memset(visited, 0, sizeof(visited));
-
-	cout << "BFS: " << endl;
-	BFS(G, 0);
-	cout << endl;
-
-	return 0;
-}