sort排序后可以扫一遍求出每个数的个数，注意强制转换

#include<iostream>
#include<algorithm>
using namespace std;
long long a[50010],z[50010];
int main()
{
    int n,i,maxn=0,now=0,top=0;
    long long sum=0;
    cin>>n;
    for(i=1;i<=n;i++)
     cin>>a[i];
    sort(a+1,a+n+1);
    for(i=1;i<=n;i++)
     {
        sum+=a[i];
        if(a[i]==a[i-1])
         now++;
        else
         now=1;
        if(now==maxn)
        {
            top++;
            z[top]=a[i];
        }
        if(now>maxn)
        {
            maxn=now;
            top=1;
            z[top]=a[i];
        }
     }
    printf("%.2lf\n",double(sum)/double(n));
    if(n&1)
     printf("%.2lf\n",double(a[n/2+1]));
    else
     printf("%.2lf\n",double(a[n/2]+a[n/2+1])/2.0);
    for(i=1;i<=top;i++)
     cout<<z[i]<<" ";
    return 0;
}

#include<stdio.h>
#include<map>
#include<algorithm>
using namespace std;
int n,s[50010],x=0;
map<int,int> q;
double v,m;
int main(){
    scanf("%d",&n);
    for(int i=0;i<n;++i) scanf("%d",s+i),v+=s[i],q[s[i]]++;
    sort(s,s+n);
    printf("%.2lf\n",v/n);
    printf("%.2lf\n",(s[n/2]+s[(n-1)/2])/2.);
    for(map<int,int>:: iterator it=q.begin();it!=q.end();it++)
        if(it->second>x) x=it->second;
    for(map<int,int>:: iterator it=q.begin();it!=q.end();it++)
        if(x==it->second) printf("%d ",it->first);
}
    

我竟然傻成给int的map重载比较符号？？？sort也不会用了。。。唉，下学期怕是要挂科。

#include<iostream>
#include <algorithm>
#include <map>
using namespace std;
map<int,int>num;
int data[50005];
int main(void){
    int m;
    cin>>m;
    double sum=0;
    for(int i=0;i<m;i++){
        cin>>data[i];
        sum+=data[i];
        num[data[i]]++;
    }
    printf("%.2lf\n",sum/m);
    sort(data,data+m);
    if(m%2){
        printf("%.2lf\n",(double)data[m/2]);
    }
    else{
        int temp=data[m/2]+data[(m-1)/2];
        printf("%.2lf\n",temp/2.);
    }
    //auto iter=num.begin();
    int max=0;
    for(auto iter=num.begin();iter!=num.end();iter++){
        if(iter->second>max){
            max=iter->second;
        }
    }
    for(auto iter=num.begin();iter!=num.end();iter++){
        if(iter->second==max){
            cout<<iter->first<<' ';
        }
    }
}

无比朴素的做法
```c++
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<iomanip>
#include<map>
using namespace std;

const int maxn = 50000 + 10;
int n;
int num[maxn];
map<int, int> cnt;
vector<int> vec, modes;
double median, mean;

int main () {
cin >> n;
for (int i = 0; i < n; i++) {
cin >> num[i];
if (!cnt.count(num[i])) {
cnt[num[i]] = 1;
vec.push_back(num[i]);
}
else cnt[num[i]]++;
mean += (double)num[i]/n;
}
sort(num, num+n);
if (n % 2 == 0) median = ((double)num[n/2-1]+num[n/2]) / 2;
else median = num[n/2];

int max_cnt = 0;
for (int i = 0; i < vec.size(); i++)
max_cnt = max(max_cnt, cnt[vec[i]]);
for (int i = 0; i < vec.size(); i++)
if (cnt[vec[i]] == max_cnt) modes.push_back(vec[i]);

sort(modes.begin(), modes.end());

cout << fixed << setprecision(2) << mean << "\n";
cout << median << "\n";
cout << modes[0];
for (int i = 1; i < modes.size(); i++)
cout << " " << modes[i];
return 0;
}
```

C++ STL 版
c++
// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。
//
#include<bits/stdc++.h>
using namespace std;
int n;
int nums[50010];
multiset<int> ms;
set<int> uniq;
int maxhit = -1;
int main() {
scanf("%d", &n);
double avg = 0;
for (int i = 0;i < n;i++)
{
scanf("%d", nums + i);
avg += nums[i];
ms.insert(nums[i]);
uniq.insert(nums[i]);
maxhit = max(maxhit,(int) ms.count(nums[i]));
}
avg /= n;
printf("%.2lf\n", avg);
sort(nums, nums + n);
if (n & 0x1)
{
printf("%.2lf\n", (double)nums[n >> 1]);
}
else
{
printf("%.2lf\n", ((double)nums[n >> 1] + nums[(n >> 1) - 1]) / 2);
}
for (set<int>::iterator ite = uniq.begin();ite !=uniq.end();ite++)
{
if (ms.count(*ite) == maxhit)printf("%d ", *ite);
}
}


Pascal AC
var n,m,i,j,t:longint;
k,s:double;
a,b:array[1..50001]of longint;
procedure qsort(l,r:longint);
var i,j,mid,p:longint;
begin
i:=l; j:=r;
mid:=a[(l+r)div 2];
repeat
while a[i]<mid do inc(i);
while a[j]>mid do dec(j);
if i<=j then
begin
p:=a[i];
a[i]:=a[j];
a[j]:=p;
inc(i);
dec(j);
end;
until i>j;
if l<j then qsort(l,j);
if i<r then qsort(i,r);
end;
begin
readln(n);
k:=0;
t:=0;
m:=0;
for i:=1 to n do
begin
read(a[i]);
k:=k+a[i];
end;
k:=k/n;
qsort(1,n);
if n mod 2=0 then
s:=(a[n div 2]+a[(n div 2)+1])/2
else s:=a[(n div 2)+1];
j:=a[1];
for i:=1 to n+1 do
if a[i]=j then inc(t)
else begin
if t=m then
b[i]:=j;
if t>m then
begin
m:=t;
fillchar(b,sizeof(b),0);
b[i]:=j;
end;
t:=1;
j:=a[i];
end;
writeln(k:0:2);
writeln(s:0:2);
for i:=1 to n+1 do
if b[i]<>0 then write(b[i],' ');
end.

本人方法还可以，顺大溜吧……@……
program exam;
var o:int64;
i,j,n,k,l,max:longint;
a,b,x:double;
d,e,f,h:array[0..100000] of longint;
procedure qt(l,r:longint);
var i,j,m,p:longint;
begin
i:=l; j:=r;
m:=d[(l+r) div 2];
repeat
while d[i]<m do inc(i);
while d[j]>m do dec(j);
if i<=j then
begin
p:=d[i]; d[i]:=d[j]; d[j]:=p;
inc(i); dec(j);
end;
until i>j;
if i<r then qt(i,r);
if l<j then qt(l,j);
end;

begin
readln(n);
o:=0;
for i:=1 to n do
begin
read(d[i]);
o:=o+d[i];
end;
a:=o/n;
for i:=1 to n do
f[i]:=1;
qt(1,n);
if n mod 2=1 then
x:=d[(n div 2)+1]
else
x:=(d[(n div 2)]+d[(n div 2)+1])/2;
e[1]:=d[1];
k:=1;
for i:=2 to n do
begin
if d[i]<>e[k] then
begin
inc(k);
e[k]:=d[i];
end
else
inc(f[k]);
end;
max:=0;
for i:=1 to k do
if f[i]>max then max:=f[i];
for i:=1 to k do
if f[i]=max then begin inc(l); h[l]:=e[i]; end;
writeln(a:0:2);
writeln(x:0:2);
for i:=1 to l-1 do
write(h[i],' ');
write(h[l]);
end.

测试数据 #0: Accepted, time = 15 ms, mem = 1100 KiB, score = 10
测试数据 #1: Accepted, time = 15 ms, mem = 1100 KiB, score = 10
测试数据 #2: Accepted, time = 15 ms, mem = 1100 KiB, score = 10
测试数据 #3: Accepted, time = 0 ms, mem = 1104 KiB, score = 10
测试数据 #4: Accepted, time = 0 ms, mem = 1100 KiB, score = 10
测试数据 #5: Accepted, time = 0 ms, mem = 1100 KiB, score = 10
测试数据 #6: Accepted, time = 15 ms, mem = 1104 KiB, score = 10
测试数据 #7: Accepted, time = 0 ms, mem = 1100 KiB, score = 10
测试数据 #8: Accepted, time = 78 ms, mem = 1104 KiB, score = 10
测试数据 #9: Accepted, time = 62 ms, mem = 1096 KiB, score = 10
Accepted, time = 200 ms, mem = 1104 KiB, score = 100
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn=50005;
double k[maxn]={0};int f[maxn]={0};
int numk;
double ave=0,mid,peo;
int main()
{
k[0]=-1.2134;
scanf("%d",&numk);
for(int i=1;i<=numk;i++)f[i]=1;
for(int i=1;i<=numk;i++){scanf("%lf",&k[i]);ave+=k[i];}ave/=numk;
sort(k+1,k+1+numk);
int maxl=1,maxst;
for(int i=1;i<=numk;i++)
{ int c=0;
if(k[i]==k[i-1])
for(int j=i-1;j<=numk;j++)
if(k[j]==k[i-1])c++;else break;
if(c>1)f[i]=c;maxl=max(maxl,c);
}printf("%.2lf\n",ave);
if(!(numk%2))printf("%.2lf\n",(k[numk/2]+k[numk/2+1])/2);
else printf("%.2lf\n",k[numk/2+1]);
for(int i=1;i<=numk;i++)
if(f[i]==maxl) printf("%.0lf ",k[i]);printf("\n");
return 0;
}

41 C:\Documents and Settings\402\My Documents\未命名1.cpp [Warning] converting to int' fromdouble'

求大牛改动
program p1742;
var a,b,c:array[1..50001] of longint;
n,time,m,e,max:longint;
q,d:real;

procedure swap(var a,b:longint);
var t:longint;
begin
t:=a;
a:=b;
b:=t;
end;
procedure qsort(s,t:longint);
var i,j,mid:longint;
begin
i:=s;j:=t; mid:=a[(s+t)div 2];
while i<=j do
begin
while (a[i]<mid) do inc(i);
while (a[j]>mid)do dec(j);
if i<=j then
begin
swap(a[i],a[j]);
inc(i);
dec(j);
end;
end;
if i<t then qsort(i,t);
if j>s then qsort(s,j);
end;

procedure getdata_and_calc;
var i:longint;
begin
readln(n);
for i:=1 to n do
begin
read(a[i]);
end;
qsort(1,n);
end;

procedure average;
var i:longint;
begin
for i:= 1 to n do
begin
e:=e+a[i];
end;
q:=e/n;
writeln(q:0:2);
end;

procedure mid;
begin
if n mod 2=1 then
writeln(a[n div 2 +1],'.00')
else
writeln((a[n div 2+1]+a[n div 2])/2:0:2);
end;

procedure max1;
var i,j,temp,k,sum,l,o:longint;

begin
j:=0;
k:=0;
sum:=0;
fillchar(b,sizeof(b),0);
for i:=1 to n do
if a[i]=a[i-1] then
inc(b[j])
else begin
inc(j);
inc(b[j]);
end;
for l:=1 to j do
if b[l]>max then
max:=b[l];
for o:=1 to j do
if b[o]=max then
begin
inc(k);
for l:=1 to o-1 do
sum:=sum+b[l];
inc(sum);
c[k]:=a[sum];
sum:=0;
end;
for i:=1 to k-1 do
write(c[i],' ');
write(c[k]);
end;

begin
getdata_and_calc;
average;
mid;
max1;
end.
编译成功

测试数据 #0: Accepted, time = 0 ms, mem = 1408 KiB, score = 10
测试数据 #1: Accepted, time = 0 ms, mem = 1412 KiB, score = 10
测试数据 #2: Accepted, time = 0 ms, mem = 1416 KiB, score = 10
测试数据 #3: Accepted, time = 0 ms, mem = 1416 KiB, score = 10
测试数据 #4: WrongAnswer, time = 11 ms, mem = 1412 KiB, score = 0
测试数据 #5: WrongAnswer, time = 11 ms, mem = 1408 KiB, score = 0
测试数据 #6: WrongAnswer, time = 0 ms, mem = 1412 KiB, score = 0
测试数据 #7: WrongAnswer, time = 0 ms, mem = 1416 KiB, score = 0
测试数据 #8: WrongAnswer, time = 421 ms, mem = 1416 KiB, score = 0
测试数据 #9: WrongAnswer, time = 31 ms, mem = 1412 KiB, score = 0
WrongAnswer, time = 474 ms, mem = 1416 KiB, score = 40

众数：排序后，记录每个数出现的个数a[i]，和个数的最大值max，相同的数第一个出现的位置bj[i]；枚举，a[i]=max就输出，max=1还要输出最后一个数

{

ID:darkgod-z

PROG:vijos P1742

HANG:PASCAL

}

var

n:longint;

a:array [1..50000] of longint;

procedure qsort(l,h:integer);

var

i,j,t,m:integer;

begin

i:=l;

j:=h;

m:=a[(i+j) div 2];

repeat

while a[i]

对于平均数，我们只需要对所有数求和再除以n即可。注意保存和的变量需要用long long或double，而不能用int（否则会越界）。若用long long的话，最后除以n的时候需要强制类型转换成double（否则"/"被编译器视为整除）。

对于中位数，我们只需要对所有数进行排序。C ++的库中提供了快速排序函数。举个例子，如果我们将n个数存在了一个int类型的数组a的a[0]~a[n-1]的位置。那么调用"sort(a, a + n);"后，n个数将从小到大排好序。然后如果n是奇数，就输出a[(n + 1) / 2]；否则输出a[n/2]和a[n/2+1]的平均值。

对于众数。我们将n个数排序后，相同的数形成连续的若干段。只需要一遍循环，统计每个数出现的次数，并且记录次数的最大值。之后再循环一遍，将所有次数等于最大值的元素输出即可。

时间复杂度：O(nlogn)

超详细题解传送门：

http://user.qzone.qq.com/1304445713/blog/1351821644

不设访问权限，没有动画，没有音乐，很整洁就一个博客而已！