最大獨立集問題
當樹中任何兩個節點間沒有邊時,獨立集就是所有二叉樹節點的子集。
現在將從一組元素中找到最長的獨立集。例如,如果元素用於形成二叉樹,那麼所有最大的子集,其中該子集中的元素彼此不連線。
輸入和輸出
Input: A binary tree.Output: Size of the Largest Independent Set is: 5
演算法
longSetSize(root)
在此演算法中,將形成二叉樹,該樹的每個節點都將儲存資料和 setSize。
輸入 − 二叉樹的根節點。
輸出 −最長集合的大小。
Begin if root = φ, then return 0 if setSize(root) ≠ 0, then setSize(root) if root has no child, then setSize(root) := 1 return setSize(root) setSizeEx := longSetSize(left(root)) + longSetSize(right(root)) //excluding root setSizeIn := 1 if left child exists, then setSizeIn := setSizeIn + longSetSize(left(left(root))) + longSetSize(left(right(root))) if right child exists, then setSizeIn := setSizeIn + longSetSize(right(left(root))) + longSetSize(right(right(root))) if setSizeIn > setSizeEx, then setSize(root) := setSizeIn else setSize(root) := setSizeEx return setSize(root) End
示例
#include <iostream>
using namespace std;
struct node {
int data;
int setSize;
node *left, *right;
};
int longSetSize(node *root) {
if (root == NULL)
return 0;
if (root->setSize != 0)
return root->setSize;
if (root->left == NULL && root->right == NULL) //when there is no child
return (root->setSize = 1);
// set size exclusive root is set size of left and set size of right
int setSizeEx = longSetSize(root->left) + longSetSize(root->right);
int setSizeIn = 1; //inclusive root node
if (root->left) //if left sub tree is present
setSizeIn += longSetSize(root->left->left) + longSetSize(root->left->right);
if (root->right) //if right sub tree is present
setSizeIn += longSetSize(root->right->left) +longSetSize(root->right->right);
root->setSize = (setSizeIn>setSizeEx)?setSizeIn:setSizeEx;
return root->setSize;
}
struct node* getNode(int data) { //create a new node with given data
node* newNode = new node;
newNode->data = data;
newNode->left = newNode->right = NULL;
newNode->setSize = 0;
return newNode;
}
int main() {
node *root = getNode(20);
root->left = getNode(8);
root->left->left = getNode(4);
root->left->right = getNode(12);
root->left->right->left = getNode(10);
root->left->right->right = getNode(14);
root->right = getNode(22);
root->right->right = getNode(25);
cout << "Size of the Largest Independent Set is: " << longSetSize(root);
}輸出
Size of the Largest Independent Set is − 5
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Output:
Size of the Largest Independent Set is: 5