一个N个整数的无序数组，给你一个数sum，求出数组中是否存在两个数，使他们的和为sum

先快速排序

#include <stdio.h>
#define count(a) sizeof(a)/sizeof(int)
int main()
{
    int s[] = {-1,0,-2,1,2,2,3,4,7,9,11,13};
    int sum = 7;
    int i   = 0;
    int j   = count(s)-1;
    int g   = 0;
    while(i!=j)
    {
        if(s[i]+s[j] > sum) j--;
        else if(s[i]+s[j] < sum) i++;
        else
        {
            g = 1;
            printf("%d+%d=%d\n",s[i],s[j],sum);
            i++;
        }
    }
    if(!g) printf("Not found!\n");
    return 0;
}