HDU1698Just a Hook(线段树 + 区间修改 + 求和）

题目链接

分析：1-N区间内初始都是1，然后q个询问，每个询问修改区间【a，b】的值为2或3或者1，统计最后整个区间的和

本来想刷刷手速，结果还是写了一个小时，第一个超时，因为输出的时候去每个区间查找了，直接输出tree[1].value就可以了 =_=

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstdio>
 using namespace std;
 const int Max = ;
 int hook[Max + ];
 struct node
 {
     int l,r;
     int value;
     int tag;
 };
 node tree[ * Max];
 void buildTree(int left, int right, int k)
 {
     tree[k].l = left;
     tree[k].r = right;
     tree[k].tag = -;
     if(left == right)
     {
         tree[k].value = ;
         return;
     }
     int mid = (left + right ) / ;
     buildTree(left, mid, k * );
     buildTree(mid + , right, k *  + );
     tree[k].value = tree[k * ].value + tree[k *  + ].value;
 }
 void upDate(int left, int right, int k, int newp)
 {
     if(tree[k].l ==left && tree[k].r == right)
     {
         tree[k].value = (right - left + ) * newp;
         tree[k].tag = newp;
         return;
     }
     if(tree[k].tag != -)
     {
         tree[k * ].tag = tree[k *  + ].tag = tree[k].tag;
         tree[k * ].value = (tree[k * ].r - tree[k * ].l + ) * tree[k].tag;
         tree[k *  + ].value = (tree[k *  + ].r - tree[k *  + ].l + ) * tree[k].tag;
         tree[k].tag = -;
     }
     int mid = (tree[k].l + tree[k].r) / ;
     if(right <= mid)
     {
         upDate(left, right, k * , newp);
     }
     else if(mid < left)
     {
         upDate(left, right, k *  + , newp);
     }
     else
     {
         upDate(left, mid, k * , newp);
         upDate(mid + , right, k *  + , newp);
     }
     tree[k].value = tree[k * ].value + tree[k *  + ].value;
 }
 int Search(int k)
 {
     if(tree[k].tag != -)
     {
         tree[k * ].tag = tree[k *  + ].tag = tree[k].tag;
         tree[k * ].value = (tree[k * ].r - tree[k * ].l + ) * tree[k].tag;
         tree[k *  + ].value = (tree[k *  + ].r - tree[k *  + ].l + ) * tree[k].tag;
         tree[k].tag = -;
     }
     if(tree[k].l == tree[k].r)
         return tree[k].value;
     return Search(k * ) + Search(k *  + );
 }
 int main()
 {
     int test,n;
     scanf("%d", &test);
     for(int t = ; t <= test; t++)
     {
         int q,a,b,newp;
         scanf("%d", &n);
         buildTree(, n, );
         scanf("%d", &q);
         for(int i = ; i <= q; i++)
         {
             scanf("%d%d%d", &a, &b, &newp);
             upDate(a, b, , newp);
         }
         printf("Case %d: The total value of the hook is %d.\n", t, tree[].value);
     }
     return ;
 }