插入排序

INSERTION-SORT(A)
1  for j ← 2 to length[A]
2       do key ← A[j]
3          ▹ Insert A[j] into the sorted sequence A[1 ‥ j - 1].
4          i ← j - 1
5          while i > 0 and A[i] > key
6              do A[i + 1] ← A[i]
7                 i ← i - 1
8          A[i + 1] ← key

时间复杂度：O（n^2) (我们通常考虑最坏情况下的复杂度）