目录
快速幂
a^n
n为奇数，转化为a*a^(n-1)
n为偶数，转化为计算b=a^(n/2),在计算b^2
a^b%m）
递归写法（a^b%m）
#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
ll a,b,m;
ll kuaisumi(ll a,ll b,ll m)
{ if(b==0) {return 1; }
if(b%2==1) {return (a%m)*kuaisumi(a,b-1,m)%m;}//b奇数
else
{
ll A=kuaisumi(a,b/2,m)%m;return A*A%m;
}
//缺一个递归出口：
}
int main()
{
scanf("%lld %lld %lld",&a,&b,&m);
printf("%lld",kuaisumi(a,b,m));
}
#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
ll a,b,m;
ll kuaisumi(ll a,ll b,ll m)
{ if(b==0) {return 1; }
if(b%2==1) {return (a%m)*kuaisumi(a,b-1,m)%m;}//b奇数
else
{
ll A=kuaisumi(a,b/2,m)%m;return A*A%m;
}
//缺一个递归出口：
}
int main()
{
scanf("%lld %lld %lld",&a,&b,&m);
printf("%lld",kuaisumi(a,b,m));
}
迭代写法
#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
ll a,b,m;
int main()
{
scanf("%lld %lld %lld",&a,&b,&m);
ll ans=1;
while(b>0)
{if(b&1) {ans=ans*a%m;b--;}
else {b/=2;a=a*a%m;
}
}
printf("%lld",ans);
}
单峰序列
左增右减，找峰顶
#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
using namespace std;
const int N=100001;int n,num[N];
int bis(int a[],int left,int right)
{
while(left<right)
{
int mid=left+(right-left)/2;
if(a[mid]>a[mid-1])
{
if(a[mid]>a[mid+1]) return mid;
else left=mid+1;
}
else right=mid-1;
}
return left;
}
int main()
{
scanf("%d",&n);for(int i=0;i<n;i++) scanf("%d",&num[i]);
printf("%d",bis(num,0,n-1));
}
预告：二分【3】 旋转数组
标签：二分,return,int,ll,单峰,kuaisumi,序列,include,lld From： https://blog.csdn.net/m0_68339197/article/details/139663910