HDU 1698 Just a Hook

还得好好理解一下...为什么注释部分去掉 不能AC ？ 知道的麻烦指导一下！

#include <stdio.h>
#define L(x) ((x) << 1)
#define R(x) ((x) << 1 | 1)
const int MAXN = 200000;
struct SegTree{
    int l,r;
    int metal;
    int value;
    bool lazy;
    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].metal = 1;
    tree[t].lazy = false;
    if(left == right){
        tree[t].value = 1;
        return;
    }
    int mid = tree[t].getMid();
    bulid(left, mid, L(t));
    bulid(mid + 1, right, R(t));
    tree[t].value = tree[L(t)].value + tree[R(t)].value;
}
void update(int left, int right, int metal, int t){
    //if(tree[t].metal == metal)
    //    return;
    if(left <= tree[t].l && right >= tree[t].r ){
        tree[t].metal = metal;
        tree[t].value = tree[t].metal * tree[t].getDis();
        tree[t].lazy = true;
        return;
    }
    if( tree[t].lazy ){
        tree[L(t)].metal = tree[R(t)].metal = tree[t].metal;
        tree[L(t)].value = tree[L(t)].getDis() * tree[L(t)].metal;
        tree[R(t)].value = tree[R(t)].getDis() * tree[R(t)].metal;
        tree[L(t)].lazy = tree[R(t)].lazy = true;
        tree[t].lazy = false;
    }
    int mid = tree[t].getMid();
    if( right <= mid ){
        update(left, right, metal, L(t));
    } else if( left > mid ){
        update(left, right, metal, R(t));
    } else {
        update(left, mid, metal, L(t));
        update(mid + 1, right, metal, R(t));
    }
    tree[t].value = tree[L(t)].value + tree[R(t)].value;
}
int main(){
    int cas, n, q;
    scanf("%d",&cas);
    for(int i = 1; i <= cas; ++i){
        scanf("%d",&n);        
        bulid(1, n, 1);
        scanf("%d",&q);
        while( q-- ){
            int x, y, z;
            scanf("%d%d%d",&x, &y, &z);
            update(x, y, z, 1);            
        }
        printf("Case %d: The total value of the hook is %d.\n",i,tree[1].value);
    }
    return 0;
}