diff --git a/thu_dsa/chp12/quicksort.cpp b/thu_dsa/chp12/quicksort.cpp
new file mode 100644
index 0000000..0c1f854
--- /dev/null
+++ b/thu_dsa/chp12/quicksort.cpp
@@ -0,0 +1,144 @@
+#include <iostream>
+#include <cassert>
+#include <random>
+#include <ctime>
+
+#define PARTITION3
+#define SCALE          ((int)2048)
+
+using namespace std;
+
+int partition1(int *src, int n, int pivot);
+int partition2(int *src, int n, int pivot);
+int partition3(int *src, int n, int pivot);
+time_t test_partition();
+time_t test_worst_case();
+
+int partition(int *src, int n, int pivot){
+#ifdef PARTITION1
+	return partition1(src, n, pivot);
+#else
+#ifdef PARTITION2
+	return partition2(src, n, pivot);
+#else
+	return partition3(src, n, pivot);
+#endif
+#endif
+}
+
+int partition1(int *src, int n, int pivot){
+	assert(n > 1 && pivot == src[0]);
+	int pos = 0, tail = n, head = 0;
+	while (1) {
+		while (--tail > pos && src[tail] >= pivot);	
+		if (tail == pos) break;
+		src[pos] = src[tail];
+		pos = tail;
+
+		while (++head < pos && src[head] <= pivot);
+		if (head == pos) break;
+		src[pos] = src[head];
+		pos = head;
+	}
+	src[pos] = pivot;
+	return pos;
+}
+
+int partition2(int *src, int n, int pivot){
+	assert(n > 1 && pivot == src[0]);
+	int pos = 0, tail = n, head = 0;
+	while (1) {
+		while (--tail > pos && src[tail] > pivot);
+		if (tail == pos) break;
+		src[pos] = src[tail];
+		pos = tail;
+
+		while (++head < pos && src[head] < pivot);
+		if (head == pos) break;
+		src[pos] = src[head];
+		pos = head;
+	}
+	src[pos] = pivot;
+	return pos;
+}
+
+int partition3(int *src, int n, int pivot){
+	assert(n > 1 && pivot == src[0]);
+	int mid = 1, current = 0, temp;
+	while(++current != n){
+		if(src[current] < pivot){
+			//swap
+			temp = src[current];
+			src[current] = src[mid];
+			src[mid] = temp;
+			++mid;
+		}
+	}
+	src[0] = src[mid - 1];
+	src[mid - 1] = pivot;
+	return mid - 1;
+}
+
+void quickSort(int *src, int n){
+	if (n == 0 || n == 1) return;
+
+	//init a pivot
+	int randpos = rand() % n;
+	int pivot = src[randpos];
+	src[randpos] = src[0];
+	src[0] = pivot;
+
+	int pos = partition(src, n, pivot);
+	quickSort(src, pos);
+	quickSort(src + pos + 1, n - pos - 1);
+}
+
+int main(){
+	srand((int)time(NULL));
+	clock_t time;
+	cout << "begin tests..." << endl;
+
+	time = test_partition();
+	cout << "test partition passed, running time: " << time << endl;
+
+	time = test_worst_case();
+	cout << "test_worst_case passed, running time:" << time << endl;
+
+	cout << "all tests passed" << endl;
+	system("pause");
+	return 0;
+}
+
+time_t test_partition(){
+	time_t start, end;
+	//generate data
+	int *src = new int[SCALE];
+	for (int ix = 0; ix != SCALE; ++ix)
+		src[ix] = rand();
+
+	start = clock();
+	quickSort(src, SCALE);
+	end = clock();
+
+	for (int ix = 0; ix != SCALE - 1; ++ix) {
+		assert(src[ix] <= src[ix + 1]);
+	}
+	return end - start;
+}
+
+//this func may cause stack overflow if SCALE if too BIG
+time_t test_worst_case(){
+	time_t start, end;
+	int *src = new int[SCALE];
+	for (int ix = 0; ix != SCALE; ++ix)
+		src[ix] = 0;
+
+	start = clock();
+	quickSort(src, SCALE);
+	end = clock();
+
+	for (int ix = 0; ix != SCALE - 1; ++ix) {
+		assert(src[ix] <= src[ix + 1]);
+	}
+	return end - start;
+}
diff --git a/thu_os/lab7_report.md b/thu_os/lab7_report.md
index b28ccb0..613650b 100644
--- a/thu_os/lab7_report.md
+++ b/thu_os/lab7_report.md
@@ -126,7 +126,7 @@ static __noinline void __up(semaphore_t *sem, uint32_t wait_state) {
 
 在`ucore`中，是使用`AND`信号量来实现哲学家就餐问题的，关于哲学家就餐问题和`AND`信号量，在[哲学家就餐问题及其实现](philosopher.md)中已经有过了描述和伪代码实现。这里就不再赘述，只是把代码贴在下面：
 
-```
+```c
 int state_sema[N]; /* 记录每个人状态的数组 */
 /* 信号量是一个特殊的整型变量 */
 semaphore_t mutex; /* 临界区互斥 */
diff --git a/words.md b/words.md
index ca90261..771164d 100644
--- a/words.md
+++ b/words.md
@@ -659,7 +659,7 @@ Some Words
 	- Thousands of ex-army officers have found lucrative jobs in private security firms.
 
 + upstart
-> (n)someone who behaves as it they were more important than they really are and who shows a lack of respect towards people who are more experienced and or older.
+> (n)someone who behaves as if they were more important than they really are and who shows a lack of respect towards people who are more experienced and or older.
 
 	- Many prefer a familiar authority figure to a yound upstart.
 
@@ -943,7 +943,7 @@ Some Words
 + accountable
 > (adj)responsible for the effects of your actions and willing to explain or be criticised for them
 
-	- The hospital should be held accountable for the quality of care if gives.
+	- The hospital should be held accountable for the quality of care it gives.
 	- Managers must be accountable to their decisions.
 	- The government should be accountable to all the people of the country.
 
@@ -978,7 +978,7 @@ Some Words
 > (v)used to say that someone dislikes someone or something very much</br>
 > (v)abide by: to accept and obey a decision, agreement etc, even though you may not agree with it
 
-	- I can's abide that man -- he's so self-satisfied.
+	- I can't abide that man -- he's so self-satisfied.
 	- You have to abide by the referee's decision.
 
 ## 3rd, October
@@ -1071,7 +1071,7 @@ Some Words
 + clamp
 > (v)to hold two things together using a clamp</br>
 > (v)to put or hold something in a position so that it cannot move</br>
-> (v)to put limits on what some is allowed to do</br>
+> (v)to put limits on what someone is allowed to do</br>
 > (v)clamp down: to take firm action to stop a particular type of crime
 
 	- She clamped her hands over her ears.
@@ -1115,3 +1115,13 @@ Some Words
 > (adj)more than is needed or wanted, unnecessary
 
 	- a modern building with no superfluous decoration
+
+## 4th, October
+
++ sanction
+> (n)official orders or laws stopping trade, communication etc with another country, as a way of forcing its leaders to make political changes</br>
+> (n)official permission, approval, or acceptance
+
+	- a resolution to impose sanctions on DPRK
+	- the threat of trade sanctions
+	- a newspaper run by citizens without the sanction of the government