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Add comparison between iteration and recursion.

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Fix the figure of tail recursion.
Fix two links.
This commit is contained in:
krahets
2023-09-12 00:56:59 +08:00
parent 2b54352bec
commit 5f814d6538
7 changed files with 184 additions and 10 deletions
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8
codes/java/chapter_computational_complexity/iteration.java
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@ -8,7 +8,7 @@ package chapter_computational_complexity;
public class iteration {
/* for 循环 */
public static int forLoop(int n) {
static int forLoop(int n) {
int res = 0;
// 循环求和 1, 2, ..., n-1, n
for (int i = 1; i <= n; i++) {
@ -18,7 +18,7 @@ public class iteration {
}
/* while 循环 */
public static int whileLoop(int n) {
static int whileLoop(int n) {
int res = 0;
int i = 1; // 初始化条件变量
// 循环求和 1, 2, ..., n-1, n
@ -30,7 +30,7 @@ public class iteration {
}
/* while 循环（两次更新） */
public static int whileLoopII(int n) {
static int whileLoopII(int n) {
int res = 0;
int i = 1; // 初始化条件变量
// 循环求和 1, 4, ...
@ -44,7 +44,7 @@ public class iteration {
}
/* 双层 for 循环 */
public static String nestedForLoop(int n) {
static String nestedForLoop(int n) {
StringBuilder res = new StringBuilder();
// 循环 i = 1, 2, ..., n-1, n
for (int i = 1; i <= n; i++) {

30
codes/java/chapter_computational_complexity/recursion.java
View File

@ -6,9 +6,11 @@
package chapter_computational_complexity;
import java.util.Stack;
public class recursion {
/* 递归 */
public static int recur(int n) {
static int recur(int n) {
// 终止条件
if (n == 1)
return 1;
@ -18,8 +20,27 @@ public class recursion {
return n + res;
}
/* 使用迭代模拟递归 */
static int forLoopRecur(int n) {
// 使用一个显式的栈来模拟系统调用栈
Stack<Integer> stack = new Stack<>();
int res = 0;
// 递：递归调用
for (int i = n; i > 0; i--) {
// 通过“入栈操作”模拟“递”
stack.push(i);
}
// 归：返回结果
while (!stack.isEmpty()) {
// 通过“出栈操作”模拟“归”
res += stack.pop();
}
// res = 1+2+3+...+n
return res;
}
/* 尾递归 */
public static int tailRecur(int n, int res) {
static int tailRecur(int n, int res) {
// 终止条件
if (n == 0)
return res;
@ -28,7 +49,7 @@ public class recursion {
}
/* 斐波那契数列：递归 */
public static int fib(int n) {
static int fib(int n) {
// 终止条件 f(1) = 0, f(2) = 1
if (n == 1 || n == 2)
return n - 1;
@ -46,6 +67,9 @@ public class recursion {
res = recur(n);
System.out.println("\n递归函数的求和结果 res = " + res);
res = forLoopRecur(n);
System.out.println("\n使用迭代模拟递归求和结果 res = " + res);
res = tailRecur(n, 0);
System.out.println("\n尾递归函数的求和结果 res = " + res);