字符串加空格

#include <iostream>
#include <cstring>
#include <algorithm>using namespace std;int main()
{string s;getline (cin, s);for (int i = 0; i < s.size(); i ++ )cout << s[i] << " ";
}

字符串插入

#include<bits/stdc++.h>
using namespace std;
string st1,st2;
char x;
int i,p;
int main()
{while(cin>>st1>>st2){p=0;x=0;for(i=0;i<=st1.size()-1;i++)if(st1[i]>x){x=st1[i];p=i;}for(i=0;i<=p;i++)cout<<st1[i];cout<<st2;for(i=p+1;i<=st1.size()-1;i++)cout<<st1[i];cout<<endl;}
}作者：垫底抽風
链接：https://www.acwing.com/solution/content/63316/
来源：AcWing
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只出现一次的字符

#include<iostream>
#include<cstdio>
#include<string>
using namespace std;
int main()
{string A;bool s=0;while(getline(cin,A)){for(int i=0;i<A.size();i++){if(A.find(A[i])==A.rfind(A[i])){cout<<A[i]<<endl;s=1;break;}}}if(s==0)cout<<"no"<<endl;return 0;
}

忽略大小写比较字符串大小

#include <iostream>
#include <cstring>
using namespace std;
int main()
{string s1, s2;getline(cin, s1);getline(cin, s2);for (int i = 0; s1[i]; i ++ ) if (s1[i] >= 'A' && s1[i] <= 'Z') s1[i] += 32;for (int i = 0; s2[i]; i ++ ) if (s2[i] >= 'A' && s2[i] <= 'Z') s2[i] += 32;for (int i = 0; s1[i] || s2[i]; i ++ ){if (s1[i] > s2[i]) {puts(">");return 0;} else if (s1[i] < s2[i]) { puts("<");return 0;}}puts("=");return 0;
}

去掉多余的空格

#include <iostream>
#include <cstring>
#include <algorithm>using namespace std;int main(){string s;getline(cin,s);string ans;for(int i=0;s[i];i++){if(s[i]!=' '){ans+=s[i];}else{ans+=' ';int j=i;while(s[j] && s[j]==' '){j++;}i=j-1;}}cout<<ans<<endl;return 0;
}