快排&归排&二分

快速排序

void quick_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int i = l - 1, j = r + 1, x = q[l + r >> 1];
    while (i < j)
    {
        do i ++ ; while (q[i] < x);
        do j -- ; while (q[j] > x);
        if (i < j) swap(q[i], q[j]);
    }

    quick_sort(q, l, j);
    quick_sort(q, j + 1, r);
}

归并排序

void merge_sort (int a[],int l,int r){
    if (l>=r) return ;
    int mid=l+r>>1;
    
    merge_sort(a,l,mid);
    merge_sort(a,mid+1,r);
    
    int k=0,i=l,j=mid+1;
    
    while(i<=mid && j<=r){
        if (a[i]<=a[j]) tmp[k++]=a[i++];
        else tmp[k++]=a[j++];
    }
    
    while(i<=mid)tmp[k++]=a[i++];
    while(j<=r) tmp[k++]=a[j++];
    
    for (int i=l,j=0;i<=r;i++,j++) a[i]=tmp[j];
}

二分

r=mid

while(l<r){
    int mid=l+r>>1;
    if (q[mid]>=x) r=mid;
    else l=mid+1;
}

l=mid

while(l<r){
    int mid=l+r+1>>1;
    if (q[mid]<=x) l=mid;
    else r=mid-1;
}