找出一堆整数中两个元素和为指定值的所有组合

#include <iostream>  
#include <algorithm>  
using namespace std;  
  
void printPairSums(int data[], int size, int sum);  
int main(int argc, char* argv[])  
{  
    int data[] = {1, 5, 9, -1, 4, 6, -2, 3, -8};  
    int size = sizeof(data) / sizeof(data[0]);  
    int i;  
    sort(data, data + size);  
    printPairSums(data, size, 8);  
  
    return 0;  
}  
void printPairSums(int data[], int size, int sum)  
{  
    int first = 0;  
    int last = size -1;  
    int s = 0;  
    while (first < last)  
    {  
        s = data[first] + data[last];  
        if (s == sum)  
        {  
            cout << data[first] << " + " << data[last] << " = " << sum << endl;  
            first++;  
            last--;  
        }  
        else if (s < sum)  
        {  
            first++;  
        }  
        else  
        {  
            last--;  
        }  
    }  
}  

#include <iostream>
#include <algorithm>
using namespace std;
void setBit(char *entry, int nBits)
{
    entry[nBits/8] = entry[nBits/8] | (1 << (nBits%8));
}
void setBit_0(char *entry, int nBits)
{
    entry[nBits/8] = entry[nBits/8] & ~(1 << (nBits%8));
}

int checkBit(char *entry, int nBits)
{
    return entry[nBits/8] & (1 << (nBits%8));
}
int main()
{
    int data[] = {5,-7, 9, -1, 1, 9, 4, 6};
    int aim = 10;
    int size = sizeof(data) / sizeof(data[0]);
    int i, min=data[0], max=data[0];
    int num_aim = 0;
    if(aim % 2 == 0)
    {
        for(i=0; i<size; i++)
        {
            if (aim / 2 == data[i])
                num_aim += 1;
        }
    }

    for(i=1; i<size; i++)
    {
        if(data[i] < min)
            min = data[i];
        if(data[i] > max)
            max = data[i];
    }
    int dis_e = (max-min) / 8 + 1;
    char entry[dis_e];
    for (i=0; i<dis_e; i++)
    {
        entry[i] = 0;
    }
    int dis = 0 - min;

    for(i=0; i<size; i++)
    {
        setBit(entry, data[i]+dis);
    }

    if(aim % 2==0)
    {
        setBit_0(entry, aim/2 + dis);
        if(num_aim > 1)
            cout << data[i] << " " << (aim - data[i]) << endl;
    }
    for(i=0; i<size; i++)
    {
        if(checkBit(entry,  aim - data[i] + dis) != 0)
        {
            setBit_0(entry, data[i] + dis);
            setBit_0(entry, aim - data[i] + dis);
            cout << data[i] << " " << (aim - data[i]) << endl;
        }
    }
}