一
#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
int cmp(int a,int b)//从大到小
{return a>b;
}void print(int *temp,int n)//打印数组
{for(int i=0;i<=n-1;i++){cout<<temp[i]<<" ";}cout<<endl;
}
int main()
{int a[10]={9,9,7,7,6,5,4,4,3,2};int b[11]={9,9,7,7,6,5,4,4,3,2,100};int *s=max_element(a,a+10);//最大元素cout<<*s<<endl;//9s=min_element(a,a+10);//最小元素cout<<*s<<endl;//2int N=unique(a,a+10)-a;//去重，返回去重后数组的尾地址cout<<N<<endl;//2print(a,N);sort(b,b+10);print(b,10);sort(b,b+10,cmp);print(b,10);///以下两个为初始化函数memset(b,0,sizeof(b)); //按位初始化，只能初始化为0 1 -1print(b,11);int x;cin>>x;fill(b,b+10,x);//按一定区间[b,b+10)初始化为xprint(b,11);return 0;
}
二
#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;int main()
{char str[5]="abcd";int len=strlen(str);cout<<str<<endl;while(next_permutation(str,str+len)){//从这个区间向后查找还有字典序吗？没有的话返回falsecout<<str<<endl;}char str1[5]="dcba";len=strlen(str1);cout<<str1<<endl;while(prev_permutation(str1,str1+len)){//从这个区间向前查找还有字典序吗？没有的话返回falsecout<<str1<<endl;}return 0;
}
三
#include<iostream>
#include<algorithm>
#include<string.h>
#include<stdio.h>
using namespace std;int main()
{int data;data=atoi("123");//a char 字符串转换成整型 同理 atol atoll atof strtoi stroll strtofcout<<data<<endl;char buf[512];sprintf(buf,"%o",data);//转换八进制,等价于buf=itoa(data);cout<<buf<<endl;//int float double long long stringint i=1750;char buffer[33];itoa(i,buffer,10);//i转换成十进制保存到字符串中printf("decimal:%s\n",buffer);itoa(i,buffer,16);//i转换成十六进制保存到字符串中printf("hexadecimal:%s\n",buffer);itoa(i,buffer,2);//i转换成二进制保存到字符串中printf("binary:%s\n",buffer);return 0;
}