/*
排序后查找问题 
Date:2017/5/12 
*/
#include<iostream>
#include<stdlib.h>
using namespace std;

int compInc(const void*a, const void*b) 
{
    return *(int *)a-*(int *)b;
}

int main()
{
    //n正整数个数， A[i] i<n保存整数 ,len:A的元素数，num总个数 
    int n,num=0;
    int A[100];
    int len=100;
    
    //读入n 
    cin>>n;
    
    //读入整数 
    for(int i=1;i<=n;i++)cin>>A[i];
    
    //先排序 
    qsort(A,len,sizeof(A[0]),compInc);
    
    //求和并检查 
    for(int x=1;x<=n;x++)
    {
        for(int y=x+1;y<=n;y++)
        {
            for(int z=y+1;z<=n;z++)
            {
                if(A[x]+A[y]==A[z]) {   num+=1; break;  }
            }
        }
    } 
    
    cout<<num;
    return 0;
} 

新手求助……想不通啊，为啥输出是零啊？？干瞪眼一晚上

#include <iostream>
using namespace std;

bool ok(int);
int number = 0;
int data[100] = {0};
int has[100] = {0};
int result = 0;
int n = 0;

int main()
{
cin>>number;
for (int i = 0; i<number; i++)
cin>>data[i];
for (int i = 0; i<number; i++)
for (int s = 0; s<number; s++)
for (int t = 0; t<number; t++)
if (data[i] == data[s] + data[t] && s != t && ok(data[i]))
{
has[n] = data[i];
result++;
n++;
}
cout<<result<<endl;

}

bool ok(int b)
{
for(int a = 0; a<100; a++)
if(has[a] == b)
return false;
return true;

}

//没啥难度，if语句原来判断没加s!=t
//数组初始化忘了用｛｝
//审题！数字个数不是组数！
//if==

#include <iostream>
#include <cstdio>
#include <string.h>
#include <cmath>
#include <algorithm>
using namespace std;
const int maxn = 105;
int a[maxn];
int b[maxn];
int main(){
int n;
scanf("%d",&n);
for(int i=0;i<n;i++){
scanf("%d",&a[i]);
}
memset(b,0,sizeof(b));
sort(a,a+n);
int cnt = 0;
for(int i=0;i<n-1;i++){
for(int j=i+1; j<n; j++){
for(int k=j+1; k<n ;k++){
if(a[i] + a[j] == a[k]&&!b[k]){
cnt++;
b[k] = 1;
}
}
}
}
cout<<cnt<<endl;
return 0;
}

#include<stdio.h>
int main()
{
    int a,b[101];
    int i,j,k,q;//小参数 
    int sum=0;
    scanf("%d",&a);
    for(i=1;i<=a;i++)
    {
        scanf("%d",&b[i]);
    }
    for(i=1;i<=a;i++)//有几个数  
    {
        for(j=1;j<=a;j++)//循环数的个数 
        {   
            q=0;
            for(k=j+1;k<=a;k++)//因为不能连自己，就是a-1次 
            {
                if(k!=i&&j!=i&&b[k]+b[j]==b[i])
                {
                    q=1;
                    break;//跳出一层for循环 
                }
            }
            if(q==1)
            {
                sum++;
                break;//同上 
            }
        }
    }
    printf("%d",sum);
}

#include <iostream>
#define max 100
using namespace std ;

int main ()
{
int a[max];
int n = 0 ;
cin >> n ;
for ( int i = 0 ; i < n ; i++ )
cin >> a[i];
int sum[max][max];
for ( int i = n-1 ; i > 0 ; i-- )
for ( int m = 0 ; m < i ; m++ )
{
sum[i][m] = a[i]+a[m];
}
int ans = 0 ;
for ( int i = 0 ; i < n ; i++ )
{
for ( int k = n-1 ; k > 0 ; k-- )
for ( int l = 0 ; l < k ; l++ )
if (a[i]==sum[k][l] )
{
i++;
k = n - 1 ;
l = 0 ;
ans++;
}
}
cout << ans;
return 0 ;
}

#include<cstdio>
#include<set>
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
int n,a[10001],vis[20002];
set<int> s;
scanf("%d",&n);
memset(vis,0,sizeof(vis));
for(int i=0;i<n;i++)
{
scanf("%d",&a[i]);
vis[a[i]]=1;
}
for(int i=0;i<n-1;i++)
{
for(int j=i+1;j<n;j++)
{
int x=a[i]+a[j];
if(vis[x])
s.insert(x);
}
}
printf("%d\n",s.size());
return 0;
}

暴力过应该也行，不过我稍稍优化了一下。
先从小到大排序，然后从第三个数字开始判断，对于每一个数字，只要枚举它前面的某两个数之和即可，枚举也有优化，也就是两头开始。比如说a b c d e,判断e的顺序是a+d,b+d,c+d,a+c,b+c,a+b，一旦满足则退出，一旦大于e则把尾数向前来一个。
```c++
#include <iostream>
#include <algorithm>
#define MAX 110
using namespace std;
int num[MAX];

int main(void)
{
int i,j,k,n,ans = 0;
cin>>n;

for(i = 0;i < n;i++)
cin>>num[i];

sort(num,num + n);

for(i = 2;i < n;i++){
for(j = i - 1;j > 0;j--){
for(k = 0;k < j;k++){
if(num[j] + num[k] == num[i]){
ans++;
j = 0;
break;
}
else if(num[j] + num[k] > num[i])
break;
}
}
}

cout<<ans<<"\n";

return 0;
}

亲们，帮我看看哪里出问题了；
#include <stdio.h>
int main(int argc, char const *argv[])
{
int n,k=0;
int a[100];
scanf("%d",&n);
for(int i=0;i<n;i++)
scanf("%d",&a[i]);
for(int i=0;i<n;i++)
{
for(int j=0;j<n-1;j++)
{
for(int t=j+1;t<n;t++)
{
if(j!=i&&t!=i&&(a[i]==a[j]+a[t]))
{
k+=1;
break;
}
}
}
}
printf("%d\n",k);
return 0;
}

#include<iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    int a[900] = {};
    int b[100000] = {};
    //cout << a[1];
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
    for (int i1 = 1; i1 < n; i1++)
    {
        for (int i2 = i1 + 1; i2 <= n; i2++)
        {
            if (a[i1] != a[i2])
            {
                int temp = (a[i1] + a[i2]);
                b[temp] = 1;
            }
        }
    }
    int sum = 0;
    for (int i3 = 1; i3 <= n; i3++)
    {
        if (b[a[i3]])
            sum += 1;
    }
    cout << sum << endl;
    //system("pause");
    return 0;
}

var
n,i,j,k:integer;
a,b:array[1..101] of 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.

md这题目哪里坑了？
#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<stdlib.h>
int n,num=0,x[109];
using namespace std;
int cmp(const void*a,const void*b)
{
return (int)a-*(int*)b;
}
int main(){
//freopen(".in","r",stdin);
//freopen(".out","w",stdout);
cin>>n;
for(int i=0;i<n;i++)
scanf("%d",&x[i]);
qsort(x,n,sizeof(x[0]),cmp);
for(int i=n-1;i>=0;i--)
for(int j=0;j<i-1;j++)
for(int z=j+1;z<i;z++)
{
if(x[z]+x[j]==x[i])
{num++;
x[i]=-2147483646;
}

}
printf("%d",num);
return 0;
}
测试数据 #0: Accepted, time = 0 ms, mem = 556 KiB, score = 10
测试数据 #1: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #2: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #3: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #4: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #5: Accepted, time = 0 ms, mem = 556 KiB, score = 10
测试数据 #6: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #7: Accepted, time = 15 ms, mem = 556 KiB, score = 10
测试数据 #8: Accepted, time = 0 ms, mem = 560 KiB, score = 10
测试数据 #9: Accepted, time = 0 ms, mem = 556 KiB, score = 10