HDU_1698_區間更新

題意：區間更新，給你一個區間a，b更新爲c值，詢問總區間的值和：

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 100000 + 10;

int cal[N<<2], sum[N<<2];

void updown(int rt, int c)
{
    if(cal[rt])
    {
        int rtt = rt << 1;
        cal[rtt] = cal[rtt+1] = cal[rt];
        sum[rtt] = (c - (c >> 1))*cal[rt];
        sum[rtt+1] = (c >> 1)*cal[rt];
        cal[rt] = 0;
    }
}

void build(int l, int r, int rt)
{
    cal[rt] = 0;
    sum[rt] = 1;
    if(l == r)
    {
        return ;
    }

    int m = (l+r) >> 1, rtt = rt << 1;
    build(l, m, rtt);
    build(m+1, r, rtt+1);
    sum[rt] = sum[rtt] + sum[rtt+1];
}

void update(int c, int L, int R, int l, int r, int rt)
{
    if(L<=l && r<=R)
    {
        cal[rt] = c;
        sum[rt] = (r-l+1) * c;
        return ;
    }

    updown(rt, r-l+1);
    int m = (l+r) >> 1, rtt = rt << 1;
    if(L <= m)    update(c, L, R, l, m, rtt);
    if(R > m)     update(c, L, R, m+1, r, rtt+1);
    sum[rt] = sum[rtt] + sum[rtt+1];
}

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

    scanf("%d", &t);

    for(int i=1; i<=t; ++i)
    {
        memset(cal, 0, sizeof(cal));
        memset(sum, 0, sizeof(sum));
        scanf("%d%d", &n, &m);

        build(1, n, 1);
        while(m--)
        {
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            update(c, a, b, 1, n, 1);
        }

        printf("Case %d: The total value of the hook is %d.\n", i, sum[1]);
    }

    return 0;
}