#include<cstdio>
#include<iostream>
using namespace std;
int n,a[110];
bool flag[10010];
int main()
{
int i,j,k,ans=0;
scanf("%d",&n);
for(i=1;i<=n;i++)
scanf("%d",&a[i]);
for(i=1;i<=n;i++)
flag[a[i]]=1;
for(i=1;i<=n;i++)
for(j=i+1;j<=n;j++)
if(a[i]+a[j]<=10000 && flag[a[i]+a[j]])
flag[a[i]+a[j]]=0,ans++;
printf("%d\n",ans);
return 0;
}

编译成功

测试数据 #0: Accepted, time = 15 ms, mem = 2512 KiB, score = 10

测试数据 #1: Accepted, time = 0 ms, mem = 2512 KiB, score = 10

测试数据 #2: Accepted, time = 0 ms, mem = 2512 KiB, score = 10

测试数据 #3: Accepted, time = 0 ms, mem = 2508 KiB, score = 10

测试数据 #4: Accepted, time = 15 ms, mem = 2508 KiB, score = 10

测试数据 #5: Accepted, time = 0 ms, mem = 2512 KiB, score = 10

测试数据 #6: Accepted, time = 0 ms, mem = 2508 KiB, score = 10

测试数据 #7: Accepted, time = 0 ms, mem = 2508 KiB, score = 10

测试数据 #8: Accepted, time = 15 ms, mem = 2508 KiB, score = 10

测试数据 #9: Accepted, time = 0 ms, mem = 2508 KiB, score = 10

Accepted, time = 45 ms, mem = 2512 KiB, score = 100

代码
#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>
#include <math.h>

using namespace std;
bool check[1000005],doublecheck[1000005];
int num[105];
int n;
int main(){
int ans = 0;
memset(check,0,sizeof(check));
memset(doublecheck,0,sizeof(doublecheck));
scanf("%d",&n);
for(int i = 1;i <= n;i ++){
scanf("%d",&num[i]);
check[num[i]] = true;
}
for(int i = 1;i <= n;i ++){
for(int j = i + 1;j <= n;j ++){
if(num[i] != num[j]){
int tmp = num[i] + num[j];
if(check[tmp] && !doublecheck[tmp]){
ans ++; doublecheck[tmp] = 1;
}
}
}
}
printf("%d\n",ans);
return 0;
}

代码乌拉拉QWQ
#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>
#include <math.h>

using namespace std;
bool check[1000005],doublecheck[1000005];
int num[105];
int n;
int main(){
int ans = 0;
memset(check,0,sizeof(check));
memset(doublecheck,0,sizeof(doublecheck));
scanf("%d",&n);
for(int i = 1;i <= n;i ++){
scanf("%d",&num[i]);
check[num[i]] = true;
}
for(int i = 1;i <= n;i ++){
for(int j = i + 1;j <= n;j ++){
if(num[i] != num[j]){
int tmp = num[i] + num[j];
if(check[tmp] && !doublecheck[tmp]){
ans ++; doublecheck[tmp] = 1;
}
}
}
}
printf("%d\n",ans);
return 0;
}

..........数据范围好像有问题。。。。。。。。。丫的。。。交了好几次才发现原来是因为数组开小了= =说好的 10000呢
#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>
#include <math.h>

using namespace std;
bool check[1000005],doublecheck[1000005];
int num[105];
int n;
int main(){
int ans = 0;
memset(check,0,sizeof(check));
memset(doublecheck,0,sizeof(doublecheck));
scanf("%d",&n);
for(int i = 1;i <= n;i ++){
scanf("%d",&num[i]);
check[num[i]] = true;
}
for(int i = 1;i <= n;i ++){
for(int j = i + 1;j <= n;j ++){
if(num[i] != num[j]){
int tmp = num[i] + num[j];
if(check[tmp] && !doublecheck[tmp]){
ans ++; doublecheck[tmp] = 1;
}
}
}
}
printf("%d\n",ans);
return 0;
}

···pascal
program sy;
var n,i,j,k,count,t:longint;
a:array[1..100]of longint;
s:array[1..100]of boolean;
begin
//fillchar(s,sizeof(s),false);
count:=0;
read(n);
for i:=1 to n do
begin
read(a[i]);
s[i]:=false;
end;
for i:=1 to n-1 do
for j:=i+1 to n do
begin
t:=a[i]+a[j];
for k:=1 to n do
if (a[k]=t)and(s[k]=false) then
begin
inc(count);
s[k]:=true;
break;
end;
end;
writeln(count);
end.
···

program sy;
var n,i,j,k,count,t:longint;
a:array[1..100]of longint;
s:array[1..100]of boolean;

begin
//fillchar(s,sizeof(s),false);

count:=0;
read(n);
for i:=1 to n do
begin
read(a[i]);
s[i]:=false;
end;
for i:=1 to n-1 do
for j:=i+1 to n do
begin
t:=a[i]+a[j];
for k:=1 to n do
if (a[k]=t)and(s[k]=false) then
begin
inc(count);
s[k]:=true;
break;
end;
end;

writeln(count);
end.

这道题要注意可能存在数据重复的情况，这种情况只能计算一次……
c
#include <stdio.h>
int n,num[110],have[100000000] = { 0 },ans = 0,cal[10000000] = { 0 };
int main(){
int i,j;
scanf("%d",&n);
for(i = 1;i<=n;i++){
scanf("%d",&num[i]);
have[num[i]] = 1;
}
for(i = 1;i<n;i++)
for(j = i+1;j<=n;j++)
if(have[num[i]+num[j]]&&!cal[num[i]+num[j]]){
ans++;cal[num[i]+num[j]] = 1;
}
printf("%d\n",ans);
return 0;
}


#include<iostream>
#include<string.h>
using namespace std;
bool check[10001];
int a[101];
int main()
{
    int i, j, n, x, t = 0;
    memset(check,false,sizeof(check));
    cin>>n;
    for (i = 0; i<n; i++)
    {
        cin>>x;
        check[x] = true;
        a[i] = x;
    }
    for (i = 0; i<n; i++)
    {
        for (j = 0; j<n; j++)
        {
            if (i!=j)
                if ((a[i] - a[j] > 0) && (a[i] - a[j] != a[j]) && (check[a[i] - a[j]]))
                {
                    t++;
                    break;                  
                }
        }
    }
    cout<<t;
    return 0;
}

#include<iostream>
#include<string.h>
using namespace std;
bool check[10001];
int a[101];
int main()
{
int i, j, n, x, t = 0;
memset(check,false,sizeof(check));
cin>>n;
for (i = 0; i<n; i++)
{
cin>>x;
check[x] = true;
a[i] = x;
}
for (i = 0; i<n; i++)
{
for (j = 0; j<n; j++)
{
if (i!=j)
if ((a[i] - a[j] > 0) && (a[i] - a[j] != a[j]) && (check[a[i] - a[j]]))
{
t++;
break;

}
}
}
cout<<t;
return 0;
}

/* ***********************************************
Author        :guanjun
Created Time  :2016/2/18 11:17:11
File Name     :vijosp1911.cpp
************************************************ */
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <iomanip>
#include <list>
#include <deque>
#include <stack>
#define ull unsigned long long
#define ll long long
#define mod 90001
#define INF 0x3f3f3f3f
#define maxn 10000+10
#define cle(a) memset(a,0,sizeof(a))
const ull inf = 1LL << 61;
const double eps=1e-5;
using namespace std;

bool cmp(int a,int b){
    return a>b;
}
int n;
int a[110];
int main()
{
    #ifndef ONLINE_JUDGE
    //freopen("in.txt","r",stdin);
    #endif
    //freopen("out.txt","w",stdout);
    while(cin>>n){
        map<int,int>mp;
        map<int,int>mp2;
        for(int i=1;i<=n;i++){
            scanf("%d",&a[i]);
            mp[a[i]]=1;
        }
        sort(a+1,a+1+n);
        int ans=0;
        for(int i=1;i<=n;i++){
            for(int j=i+1;j<=n;j++){
                int x=a[i]+a[j];
                if(mp[x]&&!mp2[x])ans++,mp2[x]=1;
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}

真想回到普及组
program p1911;
var a,b:array[1..1000]of integer;
i,j,k,n:integer;
begin
readln(n);
for i:=1 to n do read(a[i]);
for i:=1 to n do
for j:=1 to n do
for k:=j+1 to n do
if a[i]=a[j]+a[k] then b[i]:=1;
k:=0;
for i:=1 to n do
if b[i]=1 then k:=k+1;
writeln(k);
end.

program p1975;
var a:array[0..105,0..105] of char;
n,m,i,j,sum:longint;
begin
readln(n,m);
for i:=1 to n do
begin
for j:=1 to m do
read(a[i,j]);
readln;
end;
for i:=1 to n do
begin
for j:=1 to m do
if a[i,j]='*' then write('*')
else
begin
sum:=0;
if a[i-1,j-1]='*' then inc(sum);
if a[i,j-1]='*' then inc(sum);
if a[i+1,j-1]='*' then inc(sum);
if a[i-1,j+1]='*' then inc(sum);
if a[i-1,j]='*' then inc(sum);
if a[i+1,j]='*' then inc(sum);
if a[i,j+1]='*' then inc(sum);
if a[i+1,j+1]='*' then inc(sum);
write(sum);
end;
writeln;
end;
end.

1+4=5和2+3=5算一种，我被坑了，一开始全不过

#include<iostream>
#include<math.h>
#include<fstream>
using namespace std;
//ifstream in("count.in");
//ofstream out("count.out");
long int n,a[101];
int flag[101];
void read()
{
int i;
cin>>n;
for(i=1;i<=n;i++)
cin>>a[i];
}
void paixu()
{
int i,j;
for(i=1;i<=n-1;i++)
for(j=i+1;j<=n;j++)
if(a[i]>a[j])
swap(a[i],a[j]);
}
int work()
{
int i,j,k,ans=0;
for(i=3;i<=n;i++)
{
for(j=1;j<=i-2;j++)
{
for(k=j+1;k<=i-1;k++)
if(a[j]+a[k]==a[i]&&flag[i]==1)
{
flag[i]=0;
ans++;
}
}
}
return ans;
}
int main()
{
read();
paixu();
int i;
for(i=1;i<=n;i++)
flag[i]=1;
cout<<work()<<endl;
//in.close();
//out.close();
return 0;
}

正解

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
int used[100],a[100];
int i,n,m,j,k;
int main()
{
scanf("%d",&n);
for(i=1;i<=n;i++)
scanf("%d",&a[i]);
for(i=1;i<=n;i++)
for(j=1;j<=n;j++)
for(int o=1;o<=n;o++)
{
if(a[i]+a[j]==a[o]&&i!=j&&used[o]==0)
{
k++;
used[o]=1;
}
}
printf("%d\n",k);
return 0;
}
这道题要注意条件。是这样的数有几个而不是情况，比如1 2 3 4 5，,1+4=5,2+3=5，但这仅仅是一个数（5），当初没注意这一点，与一等奖交臂失之。。。

var
i,n,j,k,s:longint;
a:array[1..10000]of longint;
begin
readln(n);
for i:=1 to n do
read(a[i]);
for i:=1 to n do
for j:=1 to i-1 do
for k:=1 to n do
if i+j=k then
inc(s);
writeln(s);
end.

program eee;
var a,b:array[1..1000]of integer;
i,j,k,n:integer;
begin
readln(n);
fillchar(b,sizeof(b),0);
for i:=1 to n do read(a[i]);
for i:=1 to n do
for j:=1 to n do
for k:=j+1 to n do
if a[i]=a[j]+a[k] then b[i]:=1;
k:=0;
for i:=1 to n do
if b[i]=1 then k:=k+1;
writeln(k);
end.

Program P1911;

type gun=array [0..20000] of longint;

var n,i,j,k,len,sum:longint; a,b:gun;

function check(s,ls:longint;sb:gun):boolean;
var i:longint;
begin
if len=0 then exit(false);
for i:=1 to ls do
if sb[i]=s then exit(true);
exit(false);
end;

begin
readln(n);
for i:=1 to n do read(a[i]);
len:=0;
for i:=1 to n do
for j:=i+1 to n do begin
k:=a[i]+a[j];
if not(check(k,len,b)) then begin

{在b数组的1到len中找是否有k这个数（有:true;没有:False)}
inc(len);b[len]:=k; end;
end;
sum:=0;
for i:=1 to len do
if check(b[i],n,a) then inc(sum);
writeln(sum);
end.

do
begin
if (a[i]=x )then begin find:=true; exit; end;
end;
find:=false;
end;
begin
count:=0;
readln(n);
for i:=1 to n do
read(a[i]);
// bubbleSort(a);

for i:=1 to n do
for j:=i+1 to n do
begin k:= a[i]+a[j];
if find(a,k)=true then inc(count);
end;
writeln(count);
readln(k);
end.

include<iostream> include<cstring>

using namespace std;
int a[11000];
bool an[44100];
int main()
{
int i,j,k,n,s=0;
cin>>n;
memset(an,false,sizeof(an));
for(i=1;i<=n;i++)
cin>>a[i];
for(i=1;i<=n;i++)
{
for(j=1;j<=n;j++)
{
for(k=j+1;k<=n;k++)
{
if(a[j]+a[k]==a[i]&&an[i]==false)
{
s++;
an[i]=true;
}
}
}
}
cout<<s;
return 0;
}