hdu_4638_莫隊算法小結

先把代碼貼上留念，總結神馬的以後寫

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>

using namespace std;

const int N =100000 + 1;
int a[N], pos[N], numb, number[N];
bool flag[N];

struct node
{
    int l, r, id;
};

node sq[N];

int cmp(node a, node b)
{
    if(pos[a.l] == pos[b.l])
        return a.r < b.r;

    return pos[a.l] < pos[b.l];
}

void update(int x, bool fla)
{
    flag[x] = fla;

    if(fla)
        numb += 1-flag[x-1]-flag[x+1];

    else
        numb += flag[x-1]+flag[x+1]-1;
}

int main()
{
    int t, m, n;

    scanf("%d", &t);

    while(t--)
    {
        scanf("%d%d", &n, &m);
        memset(number, 0, sizeof(number));
        memset(flag, 0, sizeof(flag));

        int ml = ceil(sqrt(1.0*n));//分塊大小

        for(int i=1; i<=n; ++i)
        {
            scanf("%d", &a[i]);
            pos[i] = (i-1)/ml;//分塊
        }

        for(int i=0; i<m; ++i)
        {
            scanf("%d%d", &sq[i].l, &sq[i].r);
            sq[i].id = i;
        }

        sort(sq, sq+m, cmp);


        int l = 1, r = 0; numb = 0;
        for(int i=0; i<m; ++i)
        {
            int idx = sq[i].id;

            if(r < sq[i].r)
            {
                for(int j=r+1; j<=sq[i].r; ++j)
                    update(a[j], 1);
            }
            else
            {
                for(int j=r; j>sq[i].r; --j)
                    update(a[j], 0);
            }

            if(l < sq[i].l)
            {
                for(int j=l; j<sq[i].l; ++j)
                    update(a[j], 0);
            }
            else
            {
                for(int j=l-1; j>=sq[i].l; --j)
                    update(a[j], 1);
            }

            r = sq[i].r;
            l = sq[i].l;

            number[idx] = numb;
        }

        for(int i=0; i<m; ++i)
            printf("%d\n", number[i]);
    }

    return 0;
}