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T22.java
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55 lines (47 loc) · 1.32 KB
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/**
* @author aliyang
* @date 18-6-1 下午6:56
* sum-root-to-leaf-numbers：我的解法
* 思路：使用递归
* 别人思想改进：不用字符串，直接用数字，每下一层那么乘10
*/
public class T22 {
public static class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
int sum=0;
public int sumNumbers(TreeNode root) {
if (root==null)
return 0;
StringBuilder cur=new StringBuilder();
traverse(root,cur);
return sum;
}
private void traverse(TreeNode root,StringBuilder cur){
cur.append(root.val);
if (root.left==null&&root.right==null){
if (!cur.equals(""))
sum+=Integer.valueOf(cur.toString());
return;
}
if (root.left!=null){
traverse(root.left,cur);
cur.deleteCharAt(cur.length()-1);
}
if (root.right!=null){
traverse(root.right,cur);
cur.deleteCharAt(cur.length()-1);
}
}
public static void main(String[] args){
T22 t=new T22();
TreeNode root=new TreeNode(1);
TreeNode realRoot=root;
// root.left=new TreeNode(2);
root.right=new TreeNode(5);
System.out.println(t.sumNumbers(root));
}
}