@@ -630,18 +630,18 @@ public class MergeSort {
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### 2. 自顶向下归并排序
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``` java
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- public static void sort(Comparable [] a) {
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- aux = new Comparable [a. length];
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- sort(a, 0 , a. length - 1 );
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- }
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+ public static void sort(Comparable [] a) {
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+ aux = new Comparable [a. length];
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+ sort(a, 0 , a. length - 1 );
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+ }
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- private static void sort(Comparable [] a, int lo, int hi) {
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- if (hi <= lo) return ;
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- int mid = lo + (hi - lo) / 2 ;
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- sort(a, lo, mid);
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- sort(a, mid + 1 , hi);
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- merge(a, lo, mid, hi);
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- }
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+ private static void sort(Comparable [] a, int lo, int hi) {
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+ if (hi <= lo) return ;
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+ int mid = lo + (hi - lo) / 2 ;
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+ sort(a, lo, mid);
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+ sort(a, mid + 1 , hi);
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+ merge(a, lo, mid, hi);
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+ }
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```
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![ ] ( https://github.com/CyC2018/InterviewNotes/blob/master/pics/6468a541-3a9a-4008-82b6-03a0fe941d2a.png )
@@ -659,15 +659,15 @@ public class MergeSort {
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![ ] ( https://github.com/CyC2018/InterviewNotes/blob/master/pics/c7b9b4c8-83d1-4eb0-8408-ea6576a9ed90.png )
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``` java
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- public static void busort(Comparable [] a) {
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- int N = a. length;
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- aux = new Comparable [N ];
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- for (int sz = 1 ; sz < N ; sz += sz) {
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- for (int lo = 0 ; lo < N - sz; lo += sz + sz) {
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- merge(a, lo, lo + sz - 1 , Math . min(lo + sz + sz - 1 , N - 1 ));
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- }
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+ public static void busort(Comparable [] a) {
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+ int N = a. length;
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+ aux = new Comparable [N ];
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+ for (int sz = 1 ; sz < N ; sz += sz) {
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+ for (int lo = 0 ; lo < N - sz; lo += sz + sz) {
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+ merge(a, lo, lo + sz - 1 , Math . min(lo + sz + sz - 1 , N - 1 ));
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}
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}
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+ }
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```
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## 快速排序
@@ -701,18 +701,18 @@ public class QuickSort {
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![ ] ( https://github.com/CyC2018/InterviewNotes/blob/master/pics/e198c201-f386-4491-8ad6-f7e433bf992d.png )
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``` java
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- private static int partition(Comparable [] a, int lo, int hi) {
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- int i = lo, j = hi + 1 ;
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- Comparable v = a[lo];
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- while (true ) {
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- while (less(a[++ i], v)) if (i == hi) break ;
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- while (less(v, a[-- j])) if (j == lo) break ;
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- if (i >= j) break ;
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- exch(a, i, j);
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- }
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- exch(a, lo, j);
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- return j;
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- }
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+ private static int partition(Comparable [] a, int lo, int hi) {
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+ int i = lo, j = hi + 1 ;
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+ Comparable v = a[lo];
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+ while (true ) {
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+ while (less(a[++ i], v)) if (i == hi) break ;
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+ while (less(v, a[-- j])) if (j == lo) break ;
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+ if (i >= j) break ;
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+ exch(a, i, j);
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+ }
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+ exch(a, lo, j);
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+ return j;
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+ }
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```
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### 3. 性能分析
@@ -904,16 +904,16 @@ Java ϵͳ
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该算法是线性级别的,因为每次正好将数组二分,那么比较的总次数为 (N+N/2+N/4+..),直到找到第 k 个元素,这个和显然小于 2N。
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``` java
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- public static Comparable select(Comparable [] a, int k) {
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- int lo = 0 , hi = a. length - 1 ;
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- while (hi > lo) {
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- int j = partion(a, lo, hi);
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- if (j == k) return a[k];
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- else if (j > k) hi = j - 1 ;
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- else lo = j + 1 ;
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- }
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- return a[k];
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- }
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+ public static Comparable select(Comparable [] a, int k) {
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+ int lo = 0 , hi = a. length - 1 ;
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+ while (hi > lo) {
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+ int j = partion(a, lo, hi);
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+ if (j == k) return a[k];
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+ else if (j > k) hi = j - 1 ;
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+ else lo = j + 1 ;
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+ }
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+ return a[k];
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+ }
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```
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# 第三章 查找
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