HDU 3911 Black and White (segment tree interval merge)

Problem Descriptionthere is a bunch of stones on the beach; Stone color is white or black. Little Sheep have 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 was multiple cases, the first line of each case was an integer n (1<= n <= 10^5), followed by n integer 1 or 0 (1 indicates black stone and 0 indicates white stone), then was an integer M (1<=m<=10^5) followed by M operation s 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 perio D of consecutive black stones in range[i,j]
Outputwhen x=0 output A number means the longest length of black stones in range [I,j].
Sample Input

41 0 1 050 1 41 2 30 1 41 3 30 4 4

Sample Output

120

segment Tree interval merging: for RS corresponding to each interval [l,r], we give 6 quantities:lmax_1: The maximum prefix of 1 from the left, Lmax_0: The maximum prefix of 0 from the left;rmax_1: The maximum suffix of 1 from right up rmax_0: The maximum suffix of 0 on the right;max_1: The maximum continuous value of 1 of the interval, max_0: The maximum continuous value of 0 of the intervalour task is to continually update the evaluation.

#include <cstdio> #include <cstring> #include <algorithm> #include <vector> #include <string > #include <iostream> #include <queue> #include <cmath> #include <map> #include <stack>  #include <bitset>using namespace std; #define REPF (I, A, b) for (int i = A; I <= B; + + i) #define REP (i, n ) for (int i = 0; i < n; + + i) #define CLEAR (A, X) memset (A, x, sizeof a) typedef long long Ll;typedef pair& lt;int,int>pil;const int mod = 1000000007;const int maxn=1e5+10;int lmax_1[maxn<<2],rmax_1[maxn<<2]; int Lmax_0[maxn<<2],rmax_0[maxn<<2];int Max_1[maxn<<2],max_0[maxn<<2];int col[maxn< <2];int n,m,os;void pushup (int rs,int m) {lmax_1[rs]=lmax_1[rs<<1];//handles the left class prefix lmax_0[rs]=lmax_0[rs<<1    ];    if (lmax_1[rs<<1]==m-(m>>1)) lmax_1[rs]+=lmax_1[rs<<1|1];    if (lmax_0[rs<<1]==m-(m>>1)) lmax_0[rs]+=lmax_0[rs<<1|1]; rmax_1[rs]=rmax_1[rs<<1|1];//processing the right class suffix rmax_0[rs]=rmax_0[rs<<1|1];    if (rmax_1[rs<<1|1]== (m>>1)) rmax_1[rs]+=rmax_1[rs<<1];    if (rmax_0[rs<<1|1]== (m>>1)) rmax_0[rs]+=rmax_0[rs<<1]; Max_1[rs]=max (max_1[rs<<1],max_1[rs<<1|1]);//Handle the value of the entire interval Max_1[rs]=max (max_1[rs],rmax_1[rs<<1]+    LMAX_1[RS&LT;&LT;1|1]);    Max_0[rs]=max (max_0[rs<<1],max_0[rs<<1|1]); Max_0[rs]=max (max_0[rs],rmax_0[rs<<1]+lmax_0[rs<<1|1]);}    void work (int rs) {swap (lmax_1[rs],lmax_0[rs]);    Swap (Rmax_1[rs],rmax_0[rs]); Swap (Max_1[rs],max_0[rs]);}        void Push_down (int rs) {if (Col[rs]) {col[rs<<1]^=1;col[rs<<1|1]^=1;    Col[rs]=0;work (rs<<1); work (rs<<1|1);    }}void Build (int rs,int l,int r) {col[rs]=0;        if (l==r) {scanf ("%d", &os);            if (os==1) {lmax_1[rs]=rmax_1[rs]=max_1[rs]=1;        lmax_0[rs]=rmax_0[rs]=max_0[rs]=0; } else {lmax_1[rs]=rmax_1[rs]=max_1[rs]=0;        Lmax_0[rs]=rmax_0[rs]=max_0[rs]=1;    } return;    } int mid= (L+R) >>1;    Build (Rs<<1,l,mid);    Build (Rs<<1|1,mid+1,r); Pushup (rs,r-l+1);}        void update (int x,int y,int l,int r,int rs) {if (l>=x&&r<=y) {col[rs]^=1;    Work (RS);//exchange value return;    } push_down (RS);    int mid= (L+R) >>1;    if (x<=mid) update (X,Y,L,MID,RS&LT;&LT;1);    if (y>mid) update (X,Y,MID+1,R,RS&LT;&LT;1|1); Pushup (rs,r-l+1);}    int query (int x,int y,int l,int r,int rs) {if (l>=x&&r<=y) return max_1[rs];    Push_down (RS);    int mid= (L+R) >>1;    if (x>mid) return query (X,Y,MID+1,R,RS&LT;&LT;1|1);    if (y<=mid) return query (x,y,l,mid,rs<<1);    int T1=query (x,y,l,mid,rs<<1);    int T2=query (X,Y,MID+1,R,RS&LT;&LT;1|1);    int r1=min (mid-x+1,rmax_1[rs<<1]);//with mid as the dividing point int r2=min (y-mid,lmax_1[rs<<1|1]); int Res=max (max (T1,T2), r1+r2); return res;}    int main () {int op,x,y;       while (~SCANF ("%d", &n)) {build (1,1,n);       scanf ("%d", &m);           while (m--) {scanf ("%d%d%d", &op,&x,&y);           if (op==1) update (x,y,1,n,1);       else printf ("%d\n", Query (x,y,1,n,1)); }} return 0;}

HDU 3911 Black and White (segment tree interval merge)