diff --git a/README.md b/README.md
index e8821a6..2221eaa 100644
--- a/README.md
+++ b/README.md
@@ -8,16 +8,18 @@ This is my repository for the BUPT-Homework project.
 
 #### Root directory:
 
-- problem sets
-- random files I edit while in class
+- semesters
+	- problem sets
+		- solutions to the problems
 
 #### psets
 
 homeworks found at [pintia](https://pintia.cn/problem-sets?tab=1)
 
-
 ## Academic honesty
 
 I will be academically honest in all of my academic work and will not tolerate academic dishonesty of others.
 
 The commits are signed with my gpg signature and has a full history of what I have done. So I can prove that every change is done by me.
+
+The code here are only for self-study and reference, punishment for misusing the code is on your own.
diff --git a/pset1/1-add.c b/semester1/pset1/1-add.c
similarity index 100%
rename from pset1/1-add.c
rename to semester1/pset1/1-add.c
diff --git a/pset1/2-stdio.c b/semester1/pset1/2-stdio.c
similarity index 100%
rename from pset1/2-stdio.c
rename to semester1/pset1/2-stdio.c
diff --git a/pset1/3-math.c b/semester1/pset1/3-math.c
similarity index 100%
rename from pset1/3-math.c
rename to semester1/pset1/3-math.c
diff --git a/pset1/4-pi.c b/semester1/pset1/4-pi.c
similarity index 100%
rename from pset1/4-pi.c
rename to semester1/pset1/4-pi.c
diff --git a/pset1/5-data-types.c b/semester1/pset1/5-data-types.c
similarity index 100%
rename from pset1/5-data-types.c
rename to semester1/pset1/5-data-types.c
diff --git a/pset10/1-sort.c b/semester1/pset10/1-sort.c
similarity index 100%
rename from pset10/1-sort.c
rename to semester1/pset10/1-sort.c
diff --git a/pset10/2-bullet.c b/semester1/pset10/2-bullet.c
similarity index 100%
rename from pset10/2-bullet.c
rename to semester1/pset10/2-bullet.c
diff --git a/pset10/3-insertsort.c b/semester1/pset10/3-insertsort.c
similarity index 100%
rename from pset10/3-insertsort.c
rename to semester1/pset10/3-insertsort.c
diff --git a/pset10/4-shift.c b/semester1/pset10/4-shift.c
similarity index 100%
rename from pset10/4-shift.c
rename to semester1/pset10/4-shift.c
diff --git a/pset10/5-selectsort.c b/semester1/pset10/5-selectsort.c
similarity index 100%
rename from pset10/5-selectsort.c
rename to semester1/pset10/5-selectsort.c
diff --git a/pset10/6-BinarySearchIteration.c b/semester1/pset10/6-BinarySearchIteration.c
similarity index 100%
rename from pset10/6-BinarySearchIteration.c
rename to semester1/pset10/6-BinarySearchIteration.c
diff --git a/pset10/7-BinarySearchRecursion.c b/semester1/pset10/7-BinarySearchRecursion.c
similarity index 100%
rename from pset10/7-BinarySearchRecursion.c
rename to semester1/pset10/7-BinarySearchRecursion.c
diff --git a/pset11/1-1-findmin.c b/semester1/pset11/1-1-findmin.c
similarity index 100%
rename from pset11/1-1-findmin.c
rename to semester1/pset11/1-1-findmin.c
diff --git a/pset11/2-1-transpose.c b/semester1/pset11/2-1-transpose.c
similarity index 100%
rename from pset11/2-1-transpose.c
rename to semester1/pset11/2-1-transpose.c
diff --git a/pset11/2-2storage.c b/semester1/pset11/2-2storage.c
similarity index 100%
rename from pset11/2-2storage.c
rename to semester1/pset11/2-2storage.c
diff --git a/pset11/2-3-MatrixAdd.c b/semester1/pset11/2-3-MatrixAdd.c
similarity index 100%
rename from pset11/2-3-MatrixAdd.c
rename to semester1/pset11/2-3-MatrixAdd.c
diff --git a/pset11/2-4-SaddlePoint.c b/semester1/pset11/2-4-SaddlePoint.c
similarity index 100%
rename from pset11/2-4-SaddlePoint.c
rename to semester1/pset11/2-4-SaddlePoint.c
diff --git a/pset11/2-5-MatrixSort.c b/semester1/pset11/2-5-MatrixSort.c
similarity index 100%
rename from pset11/2-5-MatrixSort.c
rename to semester1/pset11/2-5-MatrixSort.c
diff --git a/pset11/2-6-SneakyMatrix.c b/semester1/pset11/2-6-SneakyMatrix.c
similarity index 100%
rename from pset11/2-6-SneakyMatrix.c
rename to semester1/pset11/2-6-SneakyMatrix.c
diff --git a/pset2/1-basketball.c b/semester1/pset2/1-basketball.c
similarity index 100%
rename from pset2/1-basketball.c
rename to semester1/pset2/1-basketball.c
diff --git a/pset2/2-num.c b/semester1/pset2/2-num.c
similarity index 100%
rename from pset2/2-num.c
rename to semester1/pset2/2-num.c
diff --git a/pset2/3-year.c b/semester1/pset2/3-year.c
similarity index 100%
rename from pset2/3-year.c
rename to semester1/pset2/3-year.c
diff --git a/pset2/4-xpr1.c b/semester1/pset2/4-xpr1.c
similarity index 100%
rename from pset2/4-xpr1.c
rename to semester1/pset2/4-xpr1.c
diff --git a/pset2/5-shopping.c b/semester1/pset2/5-shopping.c
similarity index 100%
rename from pset2/5-shopping.c
rename to semester1/pset2/5-shopping.c
diff --git a/pset2/6-triangle.c b/semester1/pset2/6-triangle.c
similarity index 100%
rename from pset2/6-triangle.c
rename to semester1/pset2/6-triangle.c
diff --git a/pset3/1-rhombus.c b/semester1/pset3/1-rhombus.c
similarity index 100%
rename from pset3/1-rhombus.c
rename to semester1/pset3/1-rhombus.c
diff --git a/pset3/2-power.c b/semester1/pset3/2-power.c
similarity index 100%
rename from pset3/2-power.c
rename to semester1/pset3/2-power.c
diff --git a/pset3/3-sum.c b/semester1/pset3/3-sum.c
similarity index 100%
rename from pset3/3-sum.c
rename to semester1/pset3/3-sum.c
diff --git a/pset3/4-count.c b/semester1/pset3/4-count.c
similarity index 100%
rename from pset3/4-count.c
rename to semester1/pset3/4-count.c
diff --git a/pset3/5-discount.c b/semester1/pset3/5-discount.c
similarity index 100%
rename from pset3/5-discount.c
rename to semester1/pset3/5-discount.c
diff --git a/pset3/6-chars.c b/semester1/pset3/6-chars.c
similarity index 100%
rename from pset3/6-chars.c
rename to semester1/pset3/6-chars.c
diff --git a/pset4/1-question.c b/semester1/pset4/1-question.c
similarity index 100%
rename from pset4/1-question.c
rename to semester1/pset4/1-question.c
diff --git a/pset4/2-ROT3.c b/semester1/pset4/2-ROT3.c
similarity index 100%
rename from pset4/2-ROT3.c
rename to semester1/pset4/2-ROT3.c
diff --git a/pset4/3-grade.c b/semester1/pset4/3-grade.c
similarity index 100%
rename from pset4/3-grade.c
rename to semester1/pset4/3-grade.c
diff --git a/pset4/4-primes.c b/semester1/pset4/4-primes.c
similarity index 100%
rename from pset4/4-primes.c
rename to semester1/pset4/4-primes.c
diff --git a/pset4/5-squares.c b/semester1/pset4/5-squares.c
similarity index 100%
rename from pset4/5-squares.c
rename to semester1/pset4/5-squares.c
diff --git a/pset4/6-graph.c b/semester1/pset4/6-graph.c
similarity index 100%
rename from pset4/6-graph.c
rename to semester1/pset4/6-graph.c
diff --git a/pset5/1-numbers.c b/semester1/pset5/1-numbers.c
similarity index 100%
rename from pset5/1-numbers.c
rename to semester1/pset5/1-numbers.c
diff --git a/pset5/2-swap.c b/semester1/pset5/2-swap.c
similarity index 100%
rename from pset5/2-swap.c
rename to semester1/pset5/2-swap.c
diff --git a/pset5/3-qualify.c b/semester1/pset5/3-qualify.c
similarity index 100%
rename from pset5/3-qualify.c
rename to semester1/pset5/3-qualify.c
diff --git a/pset5/4-isomorph.c b/semester1/pset5/4-isomorph.c
similarity index 100%
rename from pset5/4-isomorph.c
rename to semester1/pset5/4-isomorph.c
diff --git a/pset5/5-matrix.c b/semester1/pset5/5-matrix.c
similarity index 100%
rename from pset5/5-matrix.c
rename to semester1/pset5/5-matrix.c
diff --git a/pset5/6-people.c b/semester1/pset5/6-people.c
similarity index 100%
rename from pset5/6-people.c
rename to semester1/pset5/6-people.c
diff --git a/pset6/1-soldiers-table.c b/semester1/pset6/1-soldiers-table.c
similarity index 100%
rename from pset6/1-soldiers-table.c
rename to semester1/pset6/1-soldiers-table.c
diff --git a/pset6/1-soldiers.c b/semester1/pset6/1-soldiers.c
similarity index 100%
rename from pset6/1-soldiers.c
rename to semester1/pset6/1-soldiers.c
diff --git a/pset6/2-circle.c b/semester1/pset6/2-circle.c
similarity index 100%
rename from pset6/2-circle.c
rename to semester1/pset6/2-circle.c
diff --git a/pset6/3-reverse.c b/semester1/pset6/3-reverse.c
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rename from pset6/3-reverse.c
rename to semester1/pset6/3-reverse.c
diff --git a/pset6/4-binary.c b/semester1/pset6/4-binary.c
similarity index 100%
rename from pset6/4-binary.c
rename to semester1/pset6/4-binary.c
diff --git a/pset6/5-exp.c b/semester1/pset6/5-exp.c
similarity index 100%
rename from pset6/5-exp.c
rename to semester1/pset6/5-exp.c
diff --git a/pset7/1-fun.c b/semester1/pset7/1-fun.c
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rename from pset7/1-fun.c
rename to semester1/pset7/1-fun.c
diff --git a/pset7/2-getDays.c b/semester1/pset7/2-getDays.c
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rename from pset7/2-getDays.c
rename to semester1/pset7/2-getDays.c
diff --git a/pset7/3-getDigit.c b/semester1/pset7/3-getDigit.c
similarity index 100%
rename from pset7/3-getDigit.c
rename to semester1/pset7/3-getDigit.c
diff --git a/pset7/4-reverseNum.c b/semester1/pset7/4-reverseNum.c
similarity index 100%
rename from pset7/4-reverseNum.c
rename to semester1/pset7/4-reverseNum.c
diff --git a/pset7/5-myPow.c b/semester1/pset7/5-myPow.c
similarity index 100%
rename from pset7/5-myPow.c
rename to semester1/pset7/5-myPow.c
diff --git a/pset7/6-triangle.c b/semester1/pset7/6-triangle.c
similarity index 100%
rename from pset7/6-triangle.c
rename to semester1/pset7/6-triangle.c
diff --git a/pset7/7-perfect.c b/semester1/pset7/7-perfect.c
similarity index 100%
rename from pset7/7-perfect.c
rename to semester1/pset7/7-perfect.c
diff --git a/pset8/1-values.c b/semester1/pset8/1-values.c
similarity index 100%
rename from pset8/1-values.c
rename to semester1/pset8/1-values.c
diff --git a/pset8/2-getSum.c b/semester1/pset8/2-getSum.c
similarity index 100%
rename from pset8/2-getSum.c
rename to semester1/pset8/2-getSum.c
diff --git a/pset8/3-findMax.c b/semester1/pset8/3-findMax.c
similarity index 100%
rename from pset8/3-findMax.c
rename to semester1/pset8/3-findMax.c
diff --git a/pset8/4-convert.c b/semester1/pset8/4-convert.c
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rename from pset8/4-convert.c
rename to semester1/pset8/4-convert.c
diff --git a/pset8/5-countBinary.c b/semester1/pset8/5-countBinary.c
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rename from pset8/5-countBinary.c
rename to semester1/pset8/5-countBinary.c
diff --git a/pset8/6-eveluation.c b/semester1/pset8/6-eveluation.c
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rename from pset8/6-eveluation.c
rename to semester1/pset8/6-eveluation.c
diff --git a/pset8/7-gcd.c b/semester1/pset8/7-gcd.c
similarity index 100%
rename from pset8/7-gcd.c
rename to semester1/pset8/7-gcd.c
diff --git a/pset8/8-reverse.c b/semester1/pset8/8-reverse.c
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rename from pset8/8-reverse.c
rename to semester1/pset8/8-reverse.c
diff --git a/pset8/9-printFactor.c b/semester1/pset8/9-printFactor.c
similarity index 100%
rename from pset8/9-printFactor.c
rename to semester1/pset8/9-printFactor.c
diff --git a/pset9/1-avg.c b/semester1/pset9/1-avg.c
similarity index 100%
rename from pset9/1-avg.c
rename to semester1/pset9/1-avg.c
diff --git a/pset9/2-search-linear.c b/semester1/pset9/2-search-linear.c
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rename from pset9/2-search-linear.c
rename to semester1/pset9/2-search-linear.c
diff --git a/pset9/2-search.c b/semester1/pset9/2-search.c
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rename from pset9/2-search.c
rename to semester1/pset9/2-search.c
diff --git a/pset9/3-sort.c b/semester1/pset9/3-sort.c
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rename from pset9/3-sort.c
rename to semester1/pset9/3-sort.c
diff --git a/pset9/4-vector.c b/semester1/pset9/4-vector.c
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rename from pset9/4-vector.c
rename to semester1/pset9/4-vector.c
diff --git a/pset9/5-greedy.c b/semester1/pset9/5-greedy.c
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rename from pset9/5-greedy.c
rename to semester1/pset9/5-greedy.c
diff --git a/pset9/6-swap.c b/semester1/pset9/6-swap.c
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rename from pset9/6-swap.c
rename to semester1/pset9/6-swap.c
diff --git a/pset9/7-substring.c b/semester1/pset9/7-substring.c
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rename from pset9/7-substring.c
rename to semester1/pset9/7-substring.c
diff --git a/pset9/8-longest.c b/semester1/pset9/8-longest.c
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rename from pset9/8-longest.c
rename to semester1/pset9/8-longest.c