C++学习(二)

1.插入排序

#include <iostream>
using namespace std;

int main()
{
    //N数字<=10000,元素个数
    //第二行各个元素值
    //第三个表示插入的值
    int *a,N;
    cin >>N;
    a = new int[N];
    for(int i = 0;i < N;i++)
        cin >>a[i];

    //do something
    int insertValue;
    cin >> insertValue;
    if(a[0] > insertValue)
        cout <<insertValue<<" ";
    for(int i = 0;i < N;i++)
    {
        cout <<a[i]<<" ";
        if(a[i] < insertValue && a[i + 1] > insertValue)
            cout <<insertValue<<" ";

    }

    if(a[N-1] < insertValue)
        cout <<insertValue<<" ";
    cout <<endl;
    system("pause");
    return 0;
}

2.统计字符

#include <iostream>
#include <ctype.h>
using namespace std;

int main()
{
    char c;
    int alpha = 0,number = 0,space = 0,other = 0;
    while((c = getchar()) != '
')
    {
        if(isalpha(c))
            alpha++;
        else if(isdigit(c))
            number++;
        else if(c == 32)
            space++;
        else
            other++;
    }

    cout <<"letter="<<alpha<<endl;
    cout <<"space="<<space<<endl;
    cout <<"digit="<<number<<endl;
    cout <<"other="<<other<<endl;
    system("pause");
    return 0;
}

3.稀疏数组,数组的第一部分用于记录原数组的列数和行数及元素的使用个数,第二部分为原数组非零元素的行数、列数、元素值

#include <iostream>
using namespace std;

int main()
{
    //set n*n array
    int row,col,s = 0;
    cin >>row>>col;
    int **a = new int*[row];
    for(int i = 0;i < row;i++)
        a[i] = new int[col];

    //set value
    for(int i = 0;i < row;i++)
    {
        for(int j = 0;j < col;j++)
        {
            cin >> a[i][j];
            if(a[i][j] != 0)
                s++;
        }

    }
    cout <<row<<" "<<col<<" "<<s<<endl;
    //print
    for(int i = 0;i < row;i++)
    {
        for(int j = 0;j < col;j++)
        {
            if(a[i][j] != 0)
                cout <<i<<" "<<j<<" "<<a[i][j]<<endl;
        }

    }
    system("pause");
    return 0;
}

4.c++标识符和java标识符的转换

#include <iostream>
#include <string.h>
#include <ctype.h>
using namespace std;

int main()
{
    char s1[100],s2[100];
    char c;
    int r,t = 0;
    bool upper = false,line = false,firstA = false,isLineRepeat = false;
    while((c = getchar()) != '
')
    {
        if(isupper(c))
            upper = true;
        if(c == 95)
            line = true;
        if(islower(c) && t == 0)
            firstA = true;
        if(t > 0 && c == 95 && s1[t - 1] == 95)
            isLineRepeat = true;
        s1[t++] = c;
    }
    int s1_len = strlen(s1);
    if(firstA== true && line == false && upper == true)
        r = 1;
    else if(firstA == true && isLineRepeat == false && upper == false)
        r = 2;
    else
    {
        cout <<"error!"<<endl;
        system("pause");
        return 0;
    }

    if(r == 1)
    {
        cout <<"java to c++:"<<endl;
        int j = 0;
        for(int i = 0;s1[i] != '';i++,j++)
        {
            if(islower(s1[i]))
                s2[j] = s1[i];
            else
            {
                s2[j++] = '_';
                s2[j] = s1[i];
            }
        }
        s2[j] = '';
    }
    else if(r == 2)
    {
        cout <<"c++ to java:"<<endl;
        int j = 0;
        for(int i = 0;s1[i] != '';i++)
        {
            if(islower(s1[i]) )
                s2[j++] = s1[i];
            else
                s2[j++] = s1[++i] - 32;
        }
        s2[j] = '';
    }
    //print
    for(int i = 0;s2[i] != '';i++)
        cout <<s2[i];
    cout <<endl;
    system("pause");
    return 0;
}

5.5位数(找出前两位数、后两位数、中间数能被6整除)

①穷举法

#include <iostream>
using namespace std;
int main()
{
    int coutLine = 0;
    for(int i = 10000;i <= 99999;i++)
    {

        int a = i/1000;
        int b = i/100%10;
        int c = i - a*1000 - b*100;
        if(a%6==0 && b%6==0 && c%6==0)
        {
            cout <<i<<" ";
            coutLine++;
            if(coutLine%10==0)
                cout <<endl;
        }
    }
    cout <<coutLine;
    system("pause");
    return 0;
}

②找规律

#include <iostream>
using namespace std;
int main()
{
    int coutLine = 0;
    for(int a = 12;a <= 96;a+=6)
        for(int b = 0;b <= 6;b+=6)
            for(int c = 0;c <= 96;c+=6)
            {
                if(coutLine % 10 == 0)
                    cout<<endl;
                if(c < 10)
                    cout<<a<<b<<"0"<<c<<" ";
                else
                    cout <<a<<b<<c<<" ";
                coutLine++;
            }
    cout <<endl<<coutLine;
    system("pause");
    return 0;
}

6.计算n!的末尾有几个零

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >>n;
    int i = n,t = 0;
    while(i >= 5)
    {
        i = i/ 5;
        t = t+i;
    }
    cout <<t<<endl;
    system("pause");
    return 0;
}

7.最大子序列和

①方法一

#include <iostream>
using namespace std;
#define N 35000
int a[N + 1];
int main()
{
    int n;
    cin >>n;
    for(int i = 0;i < n;i++)
        cin >>a[i];

    int maxValue = 0;
    for(int i = 0;i < n;i++)
    {
        int sum = 0;
        for(int j = 0;j < n;j++)
        {
            sum += a[j];
            if(sum > maxValue)
                maxValue = sum;
        }
    }
    cout <<maxValue<<endl;
    return 0;
}

②方法二

#include <iostream>
using namespace std;
#define N 35000
int a[N + 1];
int main()
{
    //联机算法
    int n;
    cin >>n;
    for(int i = 0;i < n;i++)
         cin >>a[i];
    int nowSum = 0;
    int maxSum = 0;
    for(int i = 0;i < n;i++)
    {
        nowSum += a[i];
        if(nowSum > maxSum)
            maxSum = nowSum;
        else if(nowSum < 0)
            nowSum = 0;
    }
    cout <<maxSum<<endl;
    return 0;
}

8.抢椅子算楚谁最后第一

①方法一 时间复杂难度略高

#include <iostream>
#define N 100
using namespace std;
int a[N + 1],c = 0;
int main()
{
    int m,n;
    cin >>m>>n;
    for(int i =1;i<=m;i++)
        a[i] = 1;
    int countNumber = 0;
    int k = 1;
    while(countNumber < m -1)
    {
        for(int i = 1;i <= m;i++)
        {
            if(a[i] == 1)
            {
                if(k % n == 0)
                {
                    k = 0;
                    a[i] = 0;
                    //cout <<i<<" 0"<<endl;
                    countNumber++;
                    //cout <<countNumber<<endl;
                }
                k++;
            }
        }
    }
    for(int i = 1;i <=m;i++)
    {
        if(a[i] == 1)
            cout <<i<<endl;
    }
    system("pause");
    return 0;
}

②方法二

#include <iostream>
#define N 100
using namespace std;
int a[N + 1];
int main()
{
    int m,n;
    cin >>m>>n;
    for(int i = 1;i <= m -1;i++)
        a[i] = i+1;
    a[m] = 1;
    int countNumber = 0;
    int k = m;
    for(int i = 1;i <= m;i++)
    {
        for(int countNumber = 0;countNumber < n - 1;countNumber++)
            k = a[k];
        a[k] = a[a[k]];     //指向后一个值

    }
    cout <<k<<endl;
    system("pause");
    return 0;
}

③方法三 按规律得出公式

#include <iostream>
using namespace std;
int main()
{
    int m,n,ans = 0;
    cin >>m>>n;
    for(int i= 2;i<=m;i++)
        ans = (ans + n)%i;
    cout <<ans + 1;
    system("pause");
    return 0;
}

9.shlqsh数

#include <iostream>
using namespace std;
int main()
{
    int t1,t2;
    cin >>t1>>t2;
    int ans1 = 0,ans2 = 0;
    for(int i = 1;i < t1;i++)
        ans1 += (t1 - 1)/i;
    for(int j = 1;j <= t2;j++)
        ans2 += t2/j;
    cout <<ans2 - ans1<<endl;
    system("pause");
    return 0;
}

10.判断素数

#include <iostream>
#include <math.h>
using namespace std;
void isPrime(int x)
{
    int t = sqrt(x);
    for(int i = 2;i <= t;i++)
    {
        if(!(x % i))
        {
            cout <<x<<"不是素数!"<<endl;
            return;
        }
    }
    cout <<x<<"是素数!"<<endl;
}

int main()
{
    int a;
    cin >>a;
    if(a > 2)
        isPrime(a);
    else
        cout <<"error!"<<endl;
    system("pause");
    return 0;
}

11.哥德巴赫猜想(验证两千以内的正偶数能够分解为两个素数的和)

include <iostream>
#include <math.h>
using namespace std;
int isPrime(int x)
{
    if(x == 2)
        return 1;
    if(!(x % 2))
        return 0;
    int t = sqrt(x);
    for(int i = 3;i <= t;i++)
    {
        if(!(x % i))
            return 0;
    }
    return 1;
}

int main()
{
    for(int i = 4;i <= 2000;i+=2)
    {
        for(int j = 2;j < i;j++)
        {
            if(isPrime(j))  //a是素数
            {
                if(isPrime(i - j))  //a-j是素数
                {
                    cout <<j<<"+"<<i-j<<"="<<i<<endl;
                    break;
                }
            }
        }
    }
    system("pause");
    return 0;
}

12.逆序数

#include <iostream>
#include <math.h>
using namespace std;

int reverseNum(int x)
{
    double t = 0;
    if(x >= 10)
    {
        cout <<x%10;
        reverseNum(x/10);
    }
    else
        cout <<x<<endl;
}
int main()
{
    int a;
    cin >>a;
    reverseNum(a);
    system("pause");
    return 0;
}

13.数字转字符串

#include <iostream>
using namespace std;
void intToString(int x)
{
    int t;
    if((t = x/10)!= 0)
        intToString(x/10);
    putchar(x%10 + 48);

}
int main()
{
    int a;
    cin >>a;
    if(a < 0)
    {
        putchar('-');
        a = -a;
    }
    intToString(a);
    system("pause");
    return 0;
}

14.递归打印等边三角形

#include <iostream>
using namespace std;
void trangle(char c,int n)
{
    if(n > 0)
    {
        cout <<c;
        trangle(c,n-1);
    }
}

int main()
{
    int n;
    cin >>n;
    for(int i = 1;i<=n;i++)
    {
        trangle(' ',n - i);
        trangle('*',2*i-1);
        cout<<endl;
    }
    system("pause");
    return 0;
}