poj 3481 Double Queue
http://poj.org/problem?id=3481
第一道SBT的题,十分简单,1y。
这题用优先级来排序,查找优先级最小/最大的元素,返回其值并删除节点。
构造popHead和popTail两个函数,搜索最小/最大的节点。因为构树的时候没有构造父节点指针,所以对节点修改的函数都必须用引用符号来继承上一结点的属性。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include <cstdio> 2 #include <cstring> 3 #include <cstdlib> 4 #include <algorithm> 5 6 using namespace std; 7 8 struct SBTNode{ 9 SBTNode *left, *right; 10 int key, size, id; 11 SBTNode(int k, int i){ 12 key = k; 13 id = i; 14 size = 1; 15 left = right = NULL; 16 } 17 }; 18 19 struct SBT{ 20 SBTNode *root; 21 22 SBT(){ 23 root = NULL; 24 } 25 26 void rightRotate(SBTNode *&x){ 27 SBTNode *y = x->left; 28 29 x->left = y->right; 30 y->right = x; 31 y->size = x->size; 32 33 int ls = x->left ? x->left->size : 0; 34 int rs = x->right ? x->right->size : 0; 35 36 x->size = ls + rs + 1; 37 x = y; 38 } 39 40 void leftRotate(SBTNode *&x){ 41 SBTNode *y = x->right; 42 43 x->right = y->left; 44 y->left = x; 45 y->size = x->size; 46 47 int ls = x->left ? x->left->size : 0; 48 int rs = x->right ? x->right->size : 0; 49 50 x->size = ls + rs + 1; 51 x = y; 52 } 53 54 void maintain(SBTNode *&T, bool rightDeeper){ 55 if (!T) return ; 56 if (!rightDeeper){ 57 if (T->left == NULL) return ; 58 59 int rs = T->right ? T->right->size : 0; 60 61 if (T->left->left && T->left->left->size > rs){ 62 rightRotate(T); 63 } 64 else if (T->left->right && T->left->right->size > rs){ 65 leftRotate(T->left); 66 rightRotate(T); 67 } 68 else return ; 69 } 70 else { 71 if (T->right == NULL) return ; 72 73 int ls = T->left ? T->left->size : 0; 74 75 if (T->right->right && T->right->right->size > ls){ 76 leftRotate(T); 77 } 78 else if (T->right->left && T->right->left->size > ls){ 79 rightRotate(T->right); 80 leftRotate(T); 81 } 82 else return ; 83 } 84 maintain(T->left, false); 85 maintain(T->right, true); 86 maintain(T, false); 87 maintain(T, true); 88 } 89 90 void ins(SBTNode *&T, SBTNode *x){ 91 if (!T){ 92 T = x; 93 return ; 94 } 95 T->size++; 96 if (x->key < T->key){ 97 ins(T->left, x); 98 } 99 else{ 100 ins(T->right, x); 101 } 102 maintain(T, x->key >= T->key); 103 } 104 105 void del(SBTNode *&T, int key){ 106 if (!T) return ; 107 T->size--; 108 if (key < T->key) del(T->left, key); 109 else if (key > T->key) del(T->right, key); 110 else{ 111 SBTNode *t; 112 113 if (!T->left && !T->right){ 114 delete T; 115 T = NULL; 116 } 117 else if (!T->right){ 118 t = T; 119 T = T->left; 120 delete t; 121 } 122 else if (!T->left){ 123 t = T; 124 T = T->right; 125 delete t; 126 } 127 else{ 128 t = T->right; 129 while (t->left) t = t->left; 130 T->key = t->key; 131 T->id = t->id; 132 del(T->right, t->key); 133 } 134 } 135 } 136 137 /******the following two funtions is modeled after the delete funtion******/ 138 int popHead(SBTNode *&T){ 139 SBTNode *p = T; 140 141 if (!T) return 0; 142 T->size--; 143 if (T->left) return popHead(T->left); 144 else{ 145 T = T->right; 146 147 int ret = p->id; 148 149 delete p; 150 return ret; 151 } 152 } 153 154 int popTail(SBTNode *&T){ 155 SBTNode *p = T; 156 157 if (!T) return 0; 158 T->size--; 159 if (T->right) return popTail(T->right); 160 else{ 161 T = T->left; 162 163 int ret = p->id; 164 165 delete p; 166 return ret; 167 } 168 } 169 170 void print(SBTNode *T){ 171 if (!T) return ; 172 printf("cur %d : id %d key %d left %d right %d size %d\n", T, T->id, T->key, T->left, T->right, T->size); 173 print(T->left); 174 print(T->right); 175 } 176 }T; 177 178 void work(){ 179 int op; 180 181 T.root = NULL; 182 while (~scanf("%d", &op)){ 183 switch (op){ 184 case 1:{ 185 int id, wt; 186 187 scanf("%d%d", &id, &wt); 188 189 SBTNode *tmp = new SBTNode(wt, id); 190 T.ins(T.root, tmp); 191 //T.print(T.root); 192 } 193 break; 194 case 2:{ 195 printf("%d\n", T.popTail(T.root)); 196 //T.print(T.root); 197 } 198 break; 199 case 3:{ 200 printf("%d\n", T.popHead(T.root)); 201 //T.print(T.root); 202 } 203 break; 204 default: return ; 205 } 206 } 207 } 208 209 int main(){ 210 //freopen("in", "w", stdout); 211 work(); 212 213 return 0; 214 }
——written by Lyon