leetcode_112_路径总和@@dfs

class Solution {
    int sum;
    int tempSum=0;
    boolean flag;
    List<List<Integer>> list=new ArrayList<>();
    List<Integer> tempList=new ArrayList<>();
    public boolean hasPathSum(TreeNode root, int sum) {
        if(root==null ) return false;
        this.sum=sum;
        dfs(root);
        return flag;
    }

    public void dfs(TreeNode root){
        if(root==null) return ;
        if(root.left==null&&root.right==null){
            if((tempSum+root.val)==sum ){
               flag=true;
            }
            return ;
        }
        tempSum+=root.val;
        dfs(root.left);
        dfs(root.right);
        tempSum-=root.val;
    }
}