不好想，用桶排序解决。

int findMissingPostive(int A[], int n)      {          bucket_sort(A, n);          for (int i = 0; i < n; i++)              if (A[i] != i + 1)                  return i + 1;          return n + 1;                }      void bucket_sort(int A[], int n)      {          for (int i = 0; i < n; i++)          {              while (A[i] != i + 1)              {                  if (A[i]<=0 || A[i]>n || A[i] == A[A[i] - 1])                      break;                  swap(A[i], A[A[i] - 1]);              }          }      }