6.2 string的常见函数√

string s = "good good study";
string f = "student";
int p.= s. find(f);
if(p != -1){
    cout<<p;
}else{
    cout<<"no";
}
   

#include <bits/stdc++.h>
using namespace std;
int main() {
	string s = "this is a book";
	//截取起始下标 =第一个空格下标+1，本题=5
	//截取长度= 从第一个空格开始找第2个空格的下标
	//-第一个空格的下标 =长度
	int p1 = s. find(" ");
	int p2 = s. find(" ",p1 + 1);
	string s2 = s. substr(p1+1,p2-p1);
	cout<<s2;
	return 0;
}
	return 0;
}
   

#include <bits/stdc++. h>
using namespace std;
int main(){
    string s = "this is a book";
    //  string s2 = S. substr(5,3);
    //   cout<<s<<endl<<s2<<endl;
    s. erase(5,3);
    //this a book
    cout<<s<<endl;
    //插入is
    s. insert(5,"is ");
    cout<<s<<endl;

    //s:this is a book
    s. replace(10,4,"student");
    cout<<s<<endl;
}
   

#include <bits/stdc++. h>
using namespace std;
int main(){
    string s;
    char c;
    cin>>s>>c;
    //假删除：遍历每个字符，除了要删除的字符c以外，剩余的输出
    int i;
    for(i =0;i < s. size();i++){
        if(s[i] != c){
            cout<<s[i];
        }
    }
}
   

#include <bits/stdc++.h>
using namespace std;
int main(){
    //sdf$$$sdf
    //当s中含有要删除的字符c时，找到c的位置，并删除
    string s;
    char c;
    cin>>s>>c;
    int p = s. find(c);
    //当s 中有 c时
    while(p != -1){
        //删除s中的c
        s. erase(p,1);
        //计算s 中是否还有c
    p = s. find(c);

    }
    cout<<s;
}
   

#include <bits/stdc++. h>
using namespace std;
int main(){
    //判断每个字符是否是要替换的字符
    //如果是，则直接替换成新字符
    string s;
    char c1,c2;
    cin>>s>>c1>>c2;
    for(int i = 0;i < s. size();i++){
        if(s[i] == c1){
           s[i] = c2;
        }
    }
    cout<<s;
}

   

#include <bits/stdc++. h>
using namespace std;
int main(){
    //当s中含有字符c1时，替换为字符c2
    string s;
    string c1,c2;
    cin>>s>>c1>>c2;
    int p = s. find(c1);
    while(p != -1){
        s. replace(p,1,c2);
        p = s. find(c1);
    }
    cout<<s;
}
   

int a = 5;
if(a){
    cout<<"yes";
}else{
    cout<<"no";
}
   

int a = 0;
if(a = 5){
    cout<<"yes"<<endl;
}else{
    cout<<"no"<<endl;
}
cout<<a<<endl;
   

char c;
cin>>c;
//包含大写字母或者小写字母
//c >= 'a' && c <= 'z' | | c >= 'A' && c <= 'Z'
if(isalpha(c)){
    cout<<"字母"<<endl;
if(islower(c)){
    cout<<"小写"<<endl;
}else if(isupper(c)){
    cout<<"大写"<<endl;
}
//c >= '0' && c <= '9'
}else if(isdigit(c)){
    cout<<"数字"<<endl;
}
   

char c;
c = 'b';
//将ascii码赋值给字符，获取编码对应的字符
c = toupper(c);
cout<<c<<endl;
   

#include <bits/stdc++. h>
using namespace std;
//辅助降序排序函数
bool cmp(int a, int b){
    if(a > b){
        return true;
    }else{
        return false;
    }
}
int main(){
    int a[5]  = {3,2,1,5,4};
    int n = 5;
    sort(a,a + n);//对数组所有元素升序排序
    对数组第2个数~倒数第2个数升序排序
    sort(a+1,a+n-1);
    sort(a,a+n, cmp);//cmp 排序的方法：可以是从升序也可是降序。如果第三个参数不写，则默认的排序方法是从小到大排序。
}
   

reverse(a,a+n);
    for(int i = 0;i < n;i++){
        cout<<a[i]<<" ";
    }
}
   

string s = "jsiaszldl";
sort(s. begin(),s. end());
cout<<s;
   

#include <bits/stdc++. h>
using namespace std;
int main(){
    //使得devcpp支持sto函数
    //工具->编译选项->勾上编译时使用以下命令
    //-std=c++11
    string s = "100";
    int x = stoi(s);
    cout<<x+1<<endl;
    string s2 = "12345678912345";
    long long y = stoll(s2);
    cout<<y+1<<endl;
    string s3 = "12.34";
    float z = stof(s3);
    cout<<z + 1<<endl;
    int a = 10;
    int b = 20;
    string t1= to   string(a);
    string t2 = to   string(b);
    cout<<t1+t2<<endl;
}