二叉树之重建

二叉树之重建

输入一颗二叉树的先序遍历和中序遍历，输出它的后序遍历。

输入：

DBACEGF ABCDEFG

BCAD CBAD

输出：

ACBFGED

CDAB

var root = {value: null, left: null, right: null};
function build(root, s1, s2) {
if (s1.length === 0 || s2.length === 0 ) {
return;
}

var midnode = s2.indexOf(s1[0]);
var mleft = s2.substring(0, midnode),
mright = s2.substring(midnode + 1);
var pleft = s1.substring(1, mleft.length + 1),
pright = s1.substring(mleft.length + 1);
root.value = s1[0];
root.left = newchild();
root.right = newchild();

if(root.value) {
build(root.left, pleft, mleft);
build(root.right, pright, mright);
}
}
function newchild() {
return {value: null, left: null, right: null}
}
build(root, 'DBACEGF', 'ABCDEFG');

function postrav(root) {
if(root.value!==null){
postrav(root.left);
postrav(root.right);
console.log(root.value);
}

}
postrav(root);

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[/code]

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