POJ3468A Simple Problem with Integers（区间加数求和 + 线段树）

题目链接

题意：两种操作：一是指定区间的数全都加上一个数，二是统计指定区间的和

参考斌神的代码

 #include <iostream>
 #include <cstring>
 #include <algorithm>
 #include <cstdio>
 using namespace std;
 const int Max = ;
 const int INF = 0x3f3f3f3f;
 typedef long long LL;
 struct node
 {
     int l,r;
     LL inc; //记录这个区间所要增加的值
     LL sum;
 };
 node tree[Max * ];
 int num[Max + ];
 int n,q;
 void buildTree(int left, int right, int k)
 {
     tree[k].inc = ;
     tree[k].tag = INF;
     tree[k].l = left;
     tree[k].r = right;
     if(left == right)
     {
         tree[k].sum = num[left];
         return ;
     }
     int mid = (left + right) / ;
     buildTree(left, mid, k * );
     buildTree(mid + , right, k *  + );
     tree[k].sum = tree[k * ].sum + tree[k *  + ].sum;
 }
 void upDate(int left, int right, int k, int add)
 {
     if(tree[k].l == left && tree[k].r == right)
     {
         tree[k].inc += add; //仅仅记录一下该区间所要增加的值而已
         //tree[k].tag = add;
         return;
     }
     tree[k].sum += (right - left + ) * add; //对于这样的大区间，就要求出sum
     int mid = (tree[k].l + tree[k].r) / ;
     if(right <= mid)
     {
         upDate(left, right, k * , add);
     }
     else if(mid < left)
     {
         upDate(left, right, k *  + , add);
     }
     else
     {
         upDate(left, mid, k * , add);
         upDate(mid + , right, k *  + , add);
     }
 }
 LL Search(int left, int right, int k)
 {
     if(right < left)
         return ;
     if(left == tree[k].l && right == tree[k].r)
     {
         return tree[k].sum + (right - left + ) * tree[k].inc; //原来的和 + 增加的数的和
     }
     tree[k].sum += (tree[k].r - tree[k].l + ) * tree[k].inc;  //跟新sum的值 ,
     int mid = (tree[k].l + tree[k].r) / ;
     upDate(tree[k].l, mid, k * , tree[k].inc);
     upDate(mid + , tree[k].r, k *  + , tree[k].inc);
     tree[k].inc = ;
     if(right <= mid)
     {
         return Search(left, right, k * );
     }
     else if(mid < left)
     {
         return Search(left, right, k *  + );
     }
     else
     {
         return Search(left, mid, k * ) + Search(mid + , right, k *  + );
     }
 }
 int main()
 {
     scanf("%d%d", &n, &q);
     for(int i = ; i <= n; i++)
         scanf("%d", &num[i]);
     buildTree(, n, );
     char opt[];
     int a,b,add;
     while(q--)
     {
         scanf("%s", opt);
         if(strcmp(opt, "Q") == )
         {
             scanf("%d%d", &a, &b);

             printf("%I64d\n", Search(a, b, ));
         }
         else
         {
             scanf("%d%d%d", &a, &b, &add);
             upDate(a, b, , add);
         }
     }
     return ;
 }