hdu 3911 Black And White （线段树）

Problem Description

There are a bunch of stones on the beach; Stone color is white or black. Little Sheep has a magic brush, she can change the color of a continuous stone, black to white, white to black. Little Sheep like black very much, so she want to know the longest period of consecutive black stones in a range [i, j].

Input

There are multiple cases, the first line of each case is an integer n(1<= n <= 10^5), followed by n integer 1 or 0(1 indicates black stone and 0 indicates white stone), then is an integer M(1<=M<=10^5) followed by M operations formatted as x i j(x = 0 or 1) , x=1 means change the color of stones in range[i,j], and x=0 means ask the longest period of consecutive black stones in range[i,j]

Output

When x=0 output a number means the longest length of black stones in range [i,j].

Sample Input

4
1 0 1 0
5
0 1 4
1 2 3
0 1 4
1 3 3
0 4 4

Sample Output

1
2
0

题意

给你一些01序列，再给你一些询问。当询问为1的时候，把给定区间内所有的0变为1，1边为0，当询问为0的时候，输出所求区间中最长的连续的1的个数。

不想写题解，写这题不是要写这题，而是为了练模板……背叛指针线段树转投数组之中（但其实还是二昏二昏的）。……还有一个区间合并？

代码

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;struct Node {    int flag, lmax0, lmax1, rmax0, rmax1, imax0, imax1, l, r;   } tree[1000010];int a[1000010], n, m, x, l, r;void pushup(int root) {    int ls = root << 1, rs = root << 1 | 1;    int llen=tree[ls].r - tree[ls].l + 1;    int rlen=tree[rs].r - tree[rs].l + 1;    tree[root].lmax1=tree[ls].lmax1;    if(tree[ls].lmax1 == llen)        tree[root].lmax1 += tree[rs].lmax1;    tree[root].rmax1=tree[rs].rmax1;    if(tree[rs].rmax1 == rlen)        tree[root].rmax1 += tree[ls].rmax1;    int m1 = max(tree[ls].imax1, tree[rs].imax1);    int m2 = tree[rs].lmax1 + tree[ls].rmax1;    tree[root].imax1 = max(m1, m2);    tree[root].lmax0 = tree[ls].lmax0;    if(tree[ls].lmax0 == llen) tree[root].lmax0 += tree[rs].lmax0;    tree[root].rmax0 = tree[rs].rmax0;    if(tree[rs].rmax0 == rlen) tree[root].rmax0 += tree[ls].rmax0;    m1 = max(tree[ls].imax0, tree[rs].imax0);    m2 = tree[rs].lmax0 + tree[ls].rmax0;    tree[root].imax0 = max(m1, m2);}void pushdown(int root) {    if(tree[root].flag) {        int ls = root << 1, rs = root << 1 | 1;        tree[ls].flag ^= 1;         swap(tree[ls].lmax1, tree[ls].lmax0);        swap(tree[ls].rmax1, tree[ls].rmax0);        swap(tree[ls].imax1, tree[ls].imax0);        tree[rs].flag ^= 1;         swap(tree[rs].lmax1, tree[rs].lmax0);        swap(tree[rs].rmax1, tree[rs].rmax0);        swap(tree[rs].imax1, tree[rs].imax0);        tree[root].flag = 0;    }}void build(int root, int l, int r) {    tree[root].l = l, tree[root].r = r;    if(l == r) {        if(a[l]) {            tree[root].lmax0 = tree[root].rmax0 = tree[root].imax0 = a[l]^1;            tree[root].lmax1 = tree[root].rmax1 = tree[root].imax1 = a[l]&1;        }        else {            tree[root].lmax0 = tree[root].rmax0 = tree[root].imax0 = 1;            tree[root].lmax1 = tree[root].rmax1 = tree[root].imax1 = 0;        }        tree[root].flag = 0;        return ;    }    int mid = (l + r) >> 1;    build(root << 1, l, mid);    build(root << 1 | 1,mid + 1, r);    tree[root].flag = 0;    pushup(root);}void modify(int root, int L, int R) {    int l = tree[root].l, r = tree[root].r;    if(l >= L && r <= R) {        tree[root].flag ^= 1;        swap(tree[root].lmax1, tree[root].lmax0);        swap(tree[root].rmax1, tree[root].rmax0);        swap(tree[root].imax1, tree[root].imax0);        return ;    }    int mid = (l + r) >> 1;    pushdown(root);    if(R <= mid)        modify(root << 1, L, R);    else if(L > mid)        modify(root << 1 | 1, L, R);    else {        modify(root << 1, L, mid);        modify(root << 1 | 1, mid + 1, R);    }    pushup(root);}int query(int root,int L,int R){    int l = tree[root].l, r = tree[root].r;    if(l == L && r == R) return tree[root].imax1;    pushdown(root);    int mid = (l + r) >> 1;    if(R <= mid) return query(root << 1, L, R);    if(L > mid) return query(root << 1 | 1, L, R);    int ll = query(root << 1, L, mid);    int rl = query(root << 1 | 1, mid + 1, R);    int a = tree[root << 1].rmax1;    if(a > tree[root << 1].r - L + 1) a = tree[root << 1].r - L + 1;    int b = tree[root << 1 | 1].lmax1;    if(b > R - tree[root << 1 | 1].l + 1) b = R - tree[root << 1 | 1].l + 1;    int ans = max(ll, max(rl, a + b));    return ans;}int main() {    while(~ scanf("%d", &n)){      for(register int i = 1; i <= n; i ++)          scanf("%d", &a[i]);      build(1, 1, n);      scanf("%d", &m);      for(register int i = 1; i <= m; i ++){          scanf("%d %d %d", &x, &l, &r);          if(x == 0) printf("%d\n", query(1, l, r));          else if(x == 1) modify(1, l, r);      }    }    return 0;}