剑指Offer之Java算法习题精讲二叉树专题篇下

题目一

解法

/** * definition for a binary tree node. * public class treenode { *     int val; *     treenode left; *     treenode right; *     treenode() {} *     treenode(int val) { this.val = val; } *     treenode(int val, treenode left, treenode right) { *         this.val = val; *         this.left = left; *         this.right = right; *     } * } */class solution {    public int maxdepth(treenode root) {        return  method(root);    }    int method(treenode root){        if(root==null){            return 0;        }      梅州美食  int l = method(root.left);        int r = method(root.right);        return math.max(l, r) + 1;    }}

题目二

解法

/** * definition for a binary tree node. * public class treenode { *     int val; *     treenode left; *     treenode right; *     treenode() {} *     treenode(int val) { this.val = val; } *     treenode(int val, treenode left, treenode right) { *         this.val = val; *         this.left = left; *         this.right = right; *     } * } */class solution {    int ans = 0;    public int diameterofbinarytree(treenode root) {        method(root);        return ans;    }    public int method(treenode root){        if(root==null){            return 0;        }        int l = method(root.left);        int r = method(root.right);        ans = math.max(ans,l+r);        return math.max(l,r)+1;    }}

题目三

解法

/** * definition for a binary tree node. * public class treenode { *     int val; *     treenode left;令出如山是什么生肖 *     treenode right; *     treenode() {} *     treenode(int val) { this.val = val; } *     treenode(int val, treenode left, treenode right) { *         this.val = val; *         this.left = left; *         this.right = right; *     } * } */class solution {    public int mindepth(treenode root) {        if(root==null) return 0;        if(root.left==null&&root.right==null) return 1;        int min = integer.max_value;        if(root.left!=null){            min = math.min(min,mindepth(root.left));        }        if(root.right!=null){            min = math.min(min,mindepth(root.right));        }        return min+1;            }}

题目四

解法

/** * definition for a binary tree node. * public class treenode { *     int val; *     treenode left; *     treenode right; *     treenode() {} *     treenode(int val) { this.val = val; } *     treenode(int val, treenode left, treenode right) { *         this.val = val; *         thi学生的妈妈s.left = left; *         this.right = right; *     } * } */class solution {    list<integer> list = new arr早上好英文aylist<integer>();    public list<integer> preordertraversal(treenode root) {        method(root);   幼儿园辞职书     return list;    }    public void method(treenode root){        if(root==null){            return;        }        // 前序        list.add(root.val);        method(root.left);        // 中序        method(root.right);        // 后序    }}

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