【C++】剑指Offer上的题目1-9

// test_little_0714.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <string>
#include <random>
#include "time.h"
using namespace std;

int main(){
return 0;
}

/*
//斐波那契数列的两种方法，非递归的效率要高很多
long long Fibonacci(int N){
if (N <= 0)
return 0;
if (N == 1)
return 1;
long long arr1,arr2,arr3;
arr1 = 0;
arr2 = 1;
int times = 2;
while(times<=N){
arr3 = arr1 + arr2;
arr1 = arr2;
arr2 = arr3;
times++;
}
return arr3;
}

long long Fibonacci_r(int N){
if (N <= 0)
return 0;
if (N == 1)
return 1;
return Fibonacci_r(N - 1) + Fibonacci_r(N - 2);
}

void main(){
unsigned int N = 50;
auto tm1 = clock();
cout << Fibonacci(N) << endl;
auto tm2 = clock();
cout << "Runtime:" << 1000 * static_cast<double>(tm2 - tm1) / CLOCKS_PER_SEC << endl;
tm1 = clock();
cout << Fibonacci_r(N) << endl;
tm2 = clock();
cout << "Runtime:" << 1000 * static_cast<double>(tm2 - tm1) / CLOCKS_PER_SEC << endl;
getchar();
}
*/

/*//旋转最小序列
void move_array(int* data, int idx, int size){
int* data2 = new int[idx];
for (int i = 0; i < idx; ++i){
data2[i] = data[i];
}
for (int i = idx; i < size; i++){
data[i-idx] = data[i];
}
int num = size - idx;
for (int i = 0; i < idx; i++){
data[i+num] = data2[i];
}
delete[] data2;
}

void reverse(int* data, int length){
if (!data || length < 2)
return;
int *p1 = data;
int *p2 = data+length - 1;
while (p1!=p2){
int *temp = p1+( p2 - p1 +1 )/ 2;
if (temp == p1 || temp == p2){
p1 = (*p1 < *p2) ? p1 : p2;
}
if (*temp < *p1)
p2 = temp;
else p1 = temp;
}//二分法找到最小值
int idx = p1 - data;//最小值所在的下标位置
move_array(data, idx, length);
}

void main(){
int data[] = {3,4,5,6,7,1,2};
reverse(data, 7);
for (int i = 0; i < 7; i++)
cout << data[i] << endl;
getchar();
}*/
/*
//小范围的（如年龄）时间复杂度为O(n)的排序
void SortAges(int* ages,int length){
if (ages == nullptr || length <= 0)
return;
const int oldestAge = 99;
int timesOfAge[oldestAge + 1];
for (int i = 0; i <= oldestAge; ++i)
timesOfAge[i] = 0;
for (int i = 0; i < length; i++){
++timesOfAge[ages[i]];
}
int sum = 0;
for (int i = 0; i < 1 + oldestAge; i++){
if (timesOfAge[i] != 0){
sum += timesOfAge[i];
//注意这里的sum不会大于ages的长度，因为它表示的是出现的次数
ages[sum-1] = i;
}
}
}

void main(){
const int N = 10;
default_random_engine eng(time(0));
uniform_int_distribution<int> gen(0, 99);

int *data = new int
;
for (int i = 0; i < N; ++i){
data[i] = gen(eng);
cout << data[i] << endl;
}
cout << endl;
SortAges(data, N);
for (int i = 0; i < N; ++i)
cout << data[i] << endl;
getchar();
}

*/

/*
//快速排序
int Partition(double* dat,int size){
double thresh = dat[0];
double temp;
int i = 0;
int j = size - 1;
while (i!=j){
if (dat[j] <= thresh){
temp = dat[i+1];
dat[i] = dat[j];
dat[j] = temp;
i += 1;
}
else{
j -= 1;
}
}
dat[i] = thresh;
return i;
}

void q_sort(double* data,int size){
if (size < 2)
return;
int idx = Partition(data, size);
q_sort(data, idx);
q_sort(data + idx +1, size - idx - 1);
}

void main(){
const int N = 20;
default_random_engine eng(time(0));
uniform_real_distribution<double> gen(0, 10);

double *data = new double
;
for (int i = 0; i < N; ++i){
data[i] = gen(eng);
}
q_sort(data, N);
//Partition(data, N);
for (int i = 0; i < N; i++)
cout << data[i] <<endl;
delete[] data;
getchar();
}*/

/*
// 由前序和中序遍历结果恢复二叉树
struct treenode{
int data;
treenode* left = nullptr;
treenode* right = nullptr;
};

int find(int* p, int size, int data){
for (int i = 0; i < size; i++){
if (p[i] == data)
return i;
}
return -1;
}

treenode* construct(int *pre,int* ino,int size){
if (size < 1)
return nullptr;
treenode* head = new treenode;
head->data = pre[0];
int idx = find(ino,size,pre[0]); //左子树的节点个数
if (idx == -1)
return nullptr;
int * left_pre = pre + 1;
int * left_in = ino;
int * right_pre = pre + 1 + idx;
int * right_in = ino + 1 + idx;
head->left = construct(left_pre, left_in, idx);
head->right = construct(right_pre, right_in, size - idx - 1);
return head;
}

void PreOrder(treenode*& head){
if (head){
cout << head->data << endl;
if (head->left)
PreOrder(head->left);
if (head->right)
PreOrder(head->right);
}
}

void InOrder(treenode* &head){
if (head){
if (head->left)
InOrder(head->left);
cout << head->data << endl;
if (head->right)
InOrder(head->right);
}
}

int _tmain(int argc, _TCHAR* argv[])
{
int Preorder[] = {1,2,4,7,3,5,6,8};
int Inorder[] = {4,7,2,1,5,3,8,6};
treenode* head = construct(Preorder, Inorder, 8);
PreOrder(head);
cout << endl;
InOrder(head);
getchar();
return 0;
}

*/