POJ 3468 A Simple Problem with Integers

线段树的指针表示法。

代码还有待消化。。

代码里面多次用到了函数递归，感觉这次对递归又有了深一层的理解。

 #define LOCAL
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 using namespace std;

 struct CNode
 {
     int L, R;
     CNode *pLeft, *pRight;
     long long nSum;
     long long Inc;
 };
 CNode Tree[ + ];    //2倍叶子节点就够
 int nCount = ;
 int Mid(CNode *pRoot)
 {
     return (pRoot->L + pRoot->R) / ;
 }

 void BuildTree(CNode *pRoot, int L, int R)
 {
     pRoot->L = L;
     pRoot->R = R;
     pRoot->nSum = ;
     pRoot->Inc = ;
     if(L == R)
         return;
     ++nCount;
     pRoot->pLeft = Tree + nCount;
     ++nCount;
     pRoot->pRight = Tree + nCount;
     BuildTree(pRoot->pLeft, L, (L+R)/);
     BuildTree(pRoot->pRight, (L+R)/ + , R);
 }

 void Insert(CNode *pRoot, int i, int v)
 {
     if(pRoot->L == i && pRoot->R == i)
     {
         pRoot->nSum = v;
         return;
     }
     pRoot->nSum += v;
     if(i <= Mid(pRoot))
         Insert(pRoot->pLeft, i, v);
     else
         Insert(pRoot->pRight, i ,v);
 }

 void Add(CNode *pRoot, int a, int b, long long c)
 {
     if(pRoot->L == a && pRoot->R == b)
     {
         pRoot->Inc += c;
         return;
     }
     pRoot->nSum += (b - a + ) * c;
     if(b <= (pRoot->L + pRoot->R)/)
         Add(pRoot->pLeft, a, b, c);
     else if(a >= (pRoot->L + pRoot->R)/ + )
             Add(pRoot->pRight, a, b, c);
          else
          {
              Add(pRoot->pLeft, a, (pRoot->L + pRoot->R)/, c);
              Add(pRoot->pRight, (pRoot->L + pRoot->R)/ + , b, c);
          }
 }

 long long QuerynSum(CNode *pRoot, int a, int b)
 {
     if(pRoot->L == a && pRoot->R == b)
         return pRoot->nSum +
                 (pRoot->R - pRoot->L + ) * pRoot->Inc;

     pRoot->nSum += (pRoot->R - pRoot->L + ) * pRoot->Inc;
     Add(pRoot->pLeft, pRoot->L, Mid(pRoot), pRoot->Inc);
     Add(pRoot->pRight, Mid(pRoot) + , pRoot->R, pRoot->Inc);
     pRoot->Inc = ;
     if(b <= Mid(pRoot))
         return QuerynSum(pRoot->pLeft, a, b);
     else if(a >= Mid(pRoot) + )
             return QuerynSum(pRoot->pRight, a, b);
          else
          {
              return QuerynSum(pRoot->pLeft, a, Mid(pRoot)) +
                      QuerynSum(pRoot->pRight, Mid(pRoot) + , b);
          }
 }

 int main(void)
 {
     #ifdef LOCAL
         freopen("3468in.txt", "r", stdin);
     #endif

     int n, q, a, b, c;
     char cmd[];
     scanf("%d%d", &n, &q);
     int i, j, k;
     nCount = ;
     BuildTree(Tree, , n);
     for (i = ; i <= n; ++i)
     {
         scanf("%d", &a);
         Insert(Tree, i, a);
     }
     for(i = ; i < q; ++i)
     {
         scanf("%s", cmd);
         if(cmd[] == 'C')
         {
             scanf("%d%d%d", &a, &b, &c);
             Add(Tree, a, b, c);
         }
         else
         {
             scanf("%d%d", &a, &b);
             printf("%I64d\n", QuerynSum(Tree, a, b));
         }
     }

     return ;
 }

代码君