HDU 1540 POJ 2892 Tunnel Warfare

#include <iostream>
#include <algorithm>
#include <stack>
#define L(x) ((x) << 1)
#define R(x) ((x) << 1 | 1)
using namespace std;
const int MAXN = 50000;
struct SegTree{
    int l, r;
    int mval, lval, rval;
    int cover;    //1 没坏 0 坏 -1 有的坏了 有的没坏
    void init(int c){
        lval = rval = mval = (c == 1 ? ( r - l + 1 ) : 0);
        cover = c;         
    }
    int getMid(){
        return ( l + r ) >> 1;
    }
    int getDis(){
        return ( r - l + 1);
    }
}tree[MAXN << 2];

void bulid(int left, int right, int t){
    tree[t].l = left;
    tree[t].r = right;
    tree[t].init(1);
    if( left == right )
        return;
    int mid = tree[t].getMid();
    bulid(left, mid, L(t));
    bulid(mid + 1, right, R(t));
}

void update(int x, int c, int t){
    if(tree[t].l == tree[t].r && tree[t].l == x){
        tree[t].init(c);
        return;
    }
    if( tree[t].cover != -1 ){
        tree[L(t)].cover = tree[R(t)].cover = tree[t].cover;
        tree[L(t)].init(tree[t].cover);
        tree[R(t)].init(tree[t].cover);
    }
    int mid = tree[t].getMid();
    if( x <= mid ){
        update(x, c, L(t));
    } else {
        update(x, c, R(t));
    }
    
    tree[t].mval = max(tree[L(t)].rval + tree[R(t)].lval, max(tree[L(t)].mval, tree[R(t)].mval));
    tree[t].lval = tree[L(t)].lval + (tree[L(t)].cover == 1 ? tree[R(t)].lval : 0);
    tree[t].rval = tree[R(t)].rval + (tree[R(t)].cover == 1 ? tree[L(t)].rval : 0);
    if( tree[L(t)].cover == tree[R(t)].cover && tree[L(t)].cover != -1){    //此处无限wa 还一直找区间的问题 纠结 考虑一种情况 如果左右孩子的cover 都为-1 此时把父亲的cover也置为-1了 而我是用init 初始化 -1 传进去 则变成 0 整个区间置为空了!!!!!!!   
        tree[t].init(tree[R(t)].cover); //!!!!!!!!!!!!!!!!!!!!!!!!!
    } else {
        tree[t].cover = -1;
    }
}
int query(int x, int t){
    if( tree[t].cover == 1 )
        return tree[t].mval;
    if( tree[t]. cover == 0 )
        return 0;
    int mid = tree[t].getMid();
    if( x <= mid ){
        if( mid - x + 1 <= tree[L(t)].rval)    
            return tree[L(t)].rval + tree[R(t)].lval;
        return  query(x, L(t));
    } else {
        if( mid + tree[R(t)].lval >= x)    
            return tree[R(t)].lval + tree[L(t)].rval;
        return  query(x, R(t));
    }    
    
}
int main(){
    int n, m, x, last;
    char cmd[3];
    while( cin >> n >> m){
        bulid(1, n, 1);
        stack<int> st;
        for(int i = 0; i < m; ++i){
            cin >> cmd ;
            if( cmd[0] == 'D'){
                cin >> x;
                st.push(x);
                update(x, 0, 1);
            } else if(cmd[0] == 'Q'){
                cin >> x;
                cout << query(x, 1) << endl;
            } else if(cmd[0] == 'R'){
                if(st.empty())
                    continue;
                last = st.top();
                st.pop();
                update(last, 1, 1);
            }
        }
    }
    return 0;
}