C++ 基础语法课 - AcWing

Day 1 (2022.4.16)

bool       false/true      1byte
char       'a','\n'        1byte
int        -2^31 ~ 2^31-1  4byte
float      1.23, 1.24e2    4byte    (6-7位有效数字)
double     1.23, 1.24e2    8byte    (15-16位有效数字)  

long long  -2^63 ~ 2^63-1  8byte
long double                16byte   (18-19位有效数字)  


/ ************************************************* /

int: %d
float: %f
double: %lf
char: %c
long long: %lld


/ ************************************************* /

C++取模的符号适合前面的数有关 5%2==1, -5%2==-1

/ ************************************************* /


// cin cout 在头文件iostream
// printf scanf 在头文件cstdio

#include 

using namespace std;

int main(){
    int a, b;
    cin >> a >> b;
    cout << a + b << endl;
    return 0;
}

// 只用scanf可以不用std命名空间

#include 

int main(){
    int a, b, c, d;
    scanf("%d%d%d%d", &a, &b, &c, &d);
    printf("DIFERENCA = %d\n", a*b - c*d);
    return 0;
}

Day 2 (2022.4.17)

// string在iostream库有，且只能用cin读
// abs也在iostream库

#include 

using namespacestd;

int main(){
    double basic, sale;
    string name;
    
    cin >> name;
    scanf("%lf%lf", &sale, &basic);
    printf("TOTAL = R& %.2lf\n", basic + 0.15*sale);
    
    return 0;
}

 

#include 

using namespace std;

int main(){
    double money;
    cin >> money;
    int t = money*100;
    
    printf("NOTAS:\n");
    printf("%d nota(s) de R$ 100.00\n", t/10000); t %= 10000;
    printf("%d nota(s) de R$ 50.00\n", t/5000); t %= 5000;
    printf("%d nota(s) de R$ 20.00\n", t/2000); t %= 2000;
    printf("%d nota(s) de R$ 10.00\n", t/1000); t %= 1000;
    printf("%d nota(s) de R$ 5.00\n", t/500); t %= 500;
    printf("%d nota(s) de R$ 2.00\n", t/200); t %= 200;
    
    printf("MOEDAS:\n");
    printf("%d moeda(s) de R$ 1.00\n", t/100); t %= 100;
    printf("%d moeda(s) de R$ 0.50\n", t/50); t %= 50;
    printf("%d moeda(s) de R$ 0.25\n", t/25); t %= 25;
    printf("%d moeda(s) de R$ 0.10\n", t/10); t %= 10;
    printf("%d moeda(s) de R$ 0.05\n", t/5); t %= 5;
    printf("%d moeda(s) de R$ 0.01\n", t/1);

    
    return 0;
}

Day 3 (2022.4.18)

// min和max在algorithm，pow在cmath

#include 

using namespace std;

int main()
{
    double a, b, c;
    cin >> a >> b >> c;

    if (a < b) swap(a, b);
    if (a < c) swap(a, c);
    if (b < c) swap(b, c);

    if (a >= b + c) 
        cout << "NAO FORMA TRIANGULO" << endl;
    else
    {
        if (a * a == b * b + c * c) 
            cout << "TRIANGULO RETANGULO" << endl;
        if (a * a > b * b + c * c)
            cout << "TRIANGULO OBTUSANGULO" << endl;
        if (a * a < b * b + c * c) 
            cout << "TRIANGULO ACUTANGULO" << endl;
        if (a == b && a == c) 
            cout << "TRIANGULO EQUILATERO" << endl;
        else if (a == b || a == c || b == c) 
            cout << "TRIANGULO ISOSCELES" << endl;
    }

    return 0;
}

Day 4 (2022.4.19)

// 大多数头文件都可以用替代

// 字符串就是字符数组加上结束符'\0'
// 可以使用字符串来初始化字符数组，但由于每个字符串结尾都会含一个'\0'字符，
// 因此字符数组的长度至少要比字符串的长度多 1

char a1 = {'C', '+', '+', '\0'};
char a2[4] = "C++";

// C串的读入和输出
char s[100];
scanf("%s", s)                 //以空格分开
fgets(s, 100, stdin);          //读入一行
puts(s);                       //自动换行
printf("%s\n", s);

// string的读入和输出
string s;
getline(cin, s);
std::cout << s;

// C串的函数
strlen(a);                     //求a的长度
strcpy(a, b);                  //将b复制给a
strcmp(a, b);                  //ab返回1

//当把string对象和字符字面值及字符串字面值混在一条语句，必须确保每个加法运算符的两侧的运算对象至少有一个是string
string s1 = "12";
string s2 = '3' + "45" + s1;   //错误，不能够将字面值直接相加

// cin >> x 是会返回值的，如果读到文件末尾返回EOF
// 逗号表达式的值等于最后一个值

#include 

using namespace std;

int main(){
    int x;
    while (cin >> x, x){
        for (int i = 1; i <= x; i++) cout << i << ' ';
        cout << endl;
    }
    
    return 0;
}

// 一直读可以用代码 

while (cin >> x)
while (scanf("%d",&x)!=-1)

// scanf在读入字符时，不会自动过滤空格、回车和Tab
// 当输入为 a = 1, b = 2, 可以用scanf读入
scanf("a = %d b = %d", &a, &b)

#include 

int main(){
    int arr[10];
    for (int i=0; i<10; i++) scanf("%d", &arr[i]);
    for (int i=0; i<10; i++){
        if (arr[i]<=0) arr[i] = 1;
    }
    for (int i=0; i<10; i++) printf("X[%d] = %d\n", i, arr[i]);
    return 0;
}

Day 5 (2022.4.25)

// acwing 756. 蛇形矩阵

#include 

using namespace std;

const int N = 110;

int q[N][N];
int n, m;

int main(){
    
    cin >> n >> m;
    int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};
    int x = 0, y = 0, d = 0;
    
    for (int i=1; i<=n*m; i++){
        q[x][y] = i;
        int a = x + dx[d], b = y + dy[d];
        
        if (a>=n || a<0 || b>=m || b<0 || q[a][b]){
            d = (d + 1) % 4;
            a = x + dx[d], b = y + dy[d];
        }
        x = a, y = b;
    }
    
    for (int i=0; i

Day 6 (2022.4.26)

// AcWing 760. 字符串长度 

#include 

using namespace std;

int main(){
    string str;
    getline(cin, str);
    cout << str.size() << endl;
    return 0;
}

// AcWing 760. 字符串长度

#include 

int main(){
    char str[101];
    
    // fgets函数会把回车也读进来    
    fgets(str, 101, stdin);
    
    int len = 0;
    for (int i = 0; str[i] && str[i] != '\n'; i++) len++;
    printf("%d", len);
    return 0;
}

AcWing 763. 循环相克令

// AcWing 765. 字符串加空格
// string 默认初始化为""

#include 

using namespace std;

int main()
{
    string a, b;
    getline(cin, a);
    
    for (char c : a) b = b + c + ' ';
    // 删掉最后一个字符
    b.pop_back();
    
    cout << b;
    
    return 0;
}

// AcWing 769. 替换字符

#include 
#include 

using namespace std;

int main(){
    char str[31], c;
    scanf("%s", str);
    scanf("\n%c", &c);

    for (int i=0; str[i]; i++)
    {
        if (str[i] == c) str[i] = '#';
    }

    puts(str);
    
    return 0;
    
}

// AcWing 773. 字符串插入

#include 

using namespace std;

int main()
{
    string a, b;
    
    while (cin >> a >> b)
    {
        int p = 0;
        for (int i = 1; i < a.size(); i++)
        {
            if (a[i] > a[p]) p = i;
        }
        cout << a.substr(0, p + 1) + b + a.substr(p + 1) << endl;
    }
    
    return 0;
}

Day 7 (2022.4.27)

// AcWing 768. 忽略大小写比较字符串大小

#include 
#include 

int main()
{
    char a[100], b[100];
    
    fgets(a, 100, stdin);
    fgets(b, 100, stdin);
    
    if (a[strlen(a)-1] == '\n') a[strlen(a)-1] = 0;
    if (b[strlen(b)-1] == '\n') b[strlen(b)-1] = 0;
    
    for (int i = 0; a[i]; i++)
    {
        if (a[i] >= 'A' && a[i] <= 'Z') a[i] += 32;
    }
    
    for (int i = 0; b[i]; i++)
    {
        if (b[i] >= 'A' && b[i] <= 'Z') b[i] += 32;
    }
    
    int t = strcmp(a, b);
    if (t == 0) puts("=");
    else if (t < 0) puts("<");
    else puts(">");
    
    return 0;
}

#include 

using namespace std;

int main()
{
    string a, b;
    getline(cin, a);
    getline(cin, b);
    
    for (auto &c : a) c = tolower(c);
    for (auto &c : b) c = tolower(c);
    
    if (a == b) puts("=");
    else if (a > b) puts(">");
    else puts("<");
    
    return 0;
}

// AcWing 767. 信息加密

#include 

using namespace std;

int main()
{
    string s;

    getline(cin, s);

    for (auto &c : s)
        if (c >= 'a' && c <= 'z') c = (c - 'a' + 1) % 26 + 'a';
        else if (c >= 'A' && c <= 'Z') c = (c - 'A' + 1) % 26 + 'A';

    cout << s << endl;

    return 0;
}

Day 8 (2022.4.28)

#include 
#include 

using namespace std;

int main()
{
    string s, a, b;
    getline(cin, s);
    cin >> a >> b;
    
    stringstream ssin(s);
    string str;
    while(ssin >> str)
    {
        if (str == a) cout << b << " ";
        else cout << str << " ";
    }
    
    return 0;
}

#include 

using namespace std;

int main()
{
    int n;
    cin >> n;

    while (n -- )
    {
        string str;
        cin >> str;

        int cnt = 0;
        char c;

        for (int i = 0; i < str.size(); i ++ )
        {
            int j = i;
            while (j < str.size() && str[j] == str[i]) j ++ ;
            if (j - i > cnt) cnt = j - i, c = str[i];
            i = j - 1;
        }

        cout << c << ' ' << cnt << endl;
    }

    return 0;
}

Day 9 (2022.5.2)

// AcWing 774. 最长单词

#include 

using namespace std;

int main()
{
    string s, word;
    while(cin >> s)
    {
        if (s.back() == '.') s.pop_back();
        if (s.size() > word.size()) word = s;
    }
    
    cout << word << endl;
    
    return 0;
}

// AcWing 775. 倒排单词

#include 

using namespace std;

int main()
{
    string s[100];
    int n = 0;
    
    while(cin >> s[n]) n++;
    
    for (int i = n - 1; i>=0; i--)
    {
        cout << s[i] << ' ';
    }
    
    return 0;
}

// AcWing 776. 字符串移位包含问题

#include 
#include 

using namespace std;

int main()
{
    string a, b;
    
    cin >> a >> b;
    if (a.size() < b.size()) swap(a, b);
    
    for (int i = 0, len = a.size(); i < len; i++)
    {
        a = a.substr(1) + a[0];
        
        if (a.find(b) != string::npos)
        {
            cout << "true";
            return 0;
        }
    }
    
    cout << "false";
    return 0;
    
}

Day 10 (2022.5.8)

// 函数重载：只和函数参数（个数，类型和顺序有关）
// 传参多维数组只能省略第一维个数

// AcWing 778. 字符串最大跨距

#include 

using namespace std;

int main()
{
    string s, a, b;
    char c;
    while (cin >> c, c != ',') s += c;
    while (cin >> c, c != ',') a += c;
    while (cin >> c) b += c;
    
    int l, r;
    l = s.find(a);
    r = s.rfind(b);
    
    if (l != -1 && r != -1 && l + a.size() - 1 < r) cout << r - l - a.size();
    else cout << -1;
    
    return 0;
    
}

// AcWing 779. 最长公共字符串后缀

#include 

using namespace std;

int main()
{
    int n;
    while(cin >> n, n != 0)
    {
        int m_max = 0x3f3f3f3f;
        string s;
        cin >> s;
        
        for (int i = 1; i < n; i++)
        {
            
            int t_max = 0;
            string compare;
            cin >> compare;
            
            for (int len_s = s.size() - 1, len_com = compare.size() - 1; len_s >= 0 && len_com >= 0; len_s--, len_com--)
            {
                if (s[len_s] == compare[len_com]) t_max++;
                else break;
            }
            m_max = min(m_max, t_max);
    
        }
        
        if (m_max) cout << s.substr(s.size() - m_max) << endl;
        else cout << endl;
    
    }
    
    return 0;
}

Day 11 (2022.5.9)

// AcWing 809. 最小公倍数

#include 

using namespace std;

int gcd(int a, int b)
{
    return b ? gcd(b, a % b) : a;
}

int lcm(int a, int b)
{
    return a * b / gcd(a, b);
}

int main()
{
    int a, b;
    cin >> a >> b;
    
    cout << lcm(a, b) << endl;
    return 0;
}

// AcWing 818. 数组排序

#include 
#include 

using namespace std;

const int N = 1010;

int main()
{
    int n, l, r, a[N];
    cin >> n >> l >> r;
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a + l, a + r);
    for (int i = 0; i < n; i++) cout << a[i] << " ";
    return 0;
}

// AcWing 823. 排列

#include 

using namespace std;

int n;
const int N = 10;


void dfs(int u, int nums[], bool st[])
{
    if (u == n)
    {
        for (int i = 0; i < n; i++) cout << nums[i] << " ";
        cout << endl;
    }
    else
    {
        for (int i = 1; i <= n; i++)
        {
            if (!st[i])
            {
                nums[u] = i;
                st[i] = true;
                dfs(u + 1, nums, st);
                st[i] = false;
            }
        }
    }
}

int main()
{
    cin >> n;
    int nums[N];
    
    // 这里 {0} 是一个0初始化器
    bool st[N] = {0};
    
    dfs(0, nums, st);
    
    return 0;
}

Day 12 (2022.5.12)

// 结构体和类只有一点不同，结构体默认是public，类默认private

// 结构体初始化

struct Person
{
    int age, height;
    double money;
}

Person p = {18, 178, 100};

// 头节点一般说的是第一个节点的地址

#include 

using namespace std;

struct Node
{
    int val;
    Node* next;
    
    Node(int _val) : val(_val), next(NULL) {}
};

int main()
{
    Node node = Node(1);          // 定义一个节点
    Node* p = &node;              // 习惯用指针描述它，所以定义一个结构体指针

    Node* p = new Node(1);        // 直接生成一个结构体，返回结构体地址
}

// AcWing 35. 反转链表​

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */

class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if (!head || !head->next) return head;
        
        ListNode* p = head, *q = p->next;
        
        while(q)
        {
            ListNode* r = q->next;
            q->next = p;
            p = q, q = r;
        }
        
        head->next = NULL;
        
        return p;
    }
};

​

// AcWing 29. 删除链表中重复的节点

class Solution {
public:
    ListNode* deleteDuplication(ListNode* head) {
        ListNode *fiction = new ListNode(-1);
        fiction->next = head;
        ListNode *p = fiction;
        
        while(p->next)
        {
            ListNode *q = p->next;
            while (q->next && q->next->val == p->next->val) q = q->next;
            
            if (q == p->next) p = q;
            else p->next = q->next;
        }
        
        return fiction->next;
    }
};

Day 13 (2022.5.14)

// STL、位运算和常用库函数

        - 第8讲 STL - AcWing

 

 

 

 

 

        - 第9讲 位运算与常用库函数 - AcWing

 

 

 

// AcWing 75. 和为S的两个数字

class Solution {
public:
    vector findNumbersWithSum(vector& nums, int target) {
        unordered_set s;
        for (int x : nums)
        {
            if (s.count(target - x)) return {x, target - x};
            else s.insert(x);
        }
    }
};

// AcWing 51. 数字排列

class Solution {
public:
    vector> permutation(vector& nums) {
        sort(nums.begin(), nums.end());

        vector> res;
        do res.push_back(nums); while (next_permutation(nums.begin(), nums.end()));

        return res;
    }
};

// AcWing 862. 三元组排序

#include 
#include 
#include 

using namespace std;

struct three_Pair{
        int x;
        double y;
        string s;
        
        bool operator< (const three_Pair &t) const
        {
            return x < t.x;
        }
};

int main()
{
    three_Pair p[10001];
    int n;
    cin >> n;
    
    for (int i = 0; i < n; i++)
    {
        cin >> p[i].x >> p[i].y >> p[i].s;
    }
    
    sort(p, p+n);
    
    for (int i = 0; i < n; i++)
        printf("%d %.2lf %s\n", p[i].x, p[i].y, p[i].s.c_str());
        
    
    return 0;
}