leetcode-3Sum Closest

int cmp(const void *a,const void *b){
    return *(int *)a-*(int *)b;
}
int threeSumClosest(int* num, int numsSize, int target) {
    qsort(num,numsSize,sizeof(num[0]),cmp);
    int ret; 
    int min_err=-1;
    for(int i=0; i<numsSize; i++){
        if (i > 0 && num[i]==num[i-1])
            continue;
        int j,k;
        j = i+1;
        k = numsSize-1;
        while (j<k) {
            if (j>i+1 && num[j]==num[j-1]) { 
                j++;                    
                continue;
            }
            if (k<numsSize-1 && num[k]==num[k+1]) {
                k--;
                continue;
            }
            int err = num[i] + num[j] + num[k]-target;
            if (min_err==-1||abs(err)<min_err) {
                min_err=abs(err);
                ret=num[i] + num[j] + num[k];
                if(err==0) return ret;
            }
            if(err>0){
                k--;
            }else{
                j++;
            }
            
        }
    }
    return ret;
}