POJ 2255 Tree Recovery

思路：递归左子树、右子树

 

#include<iostream>
#include<assert.h>
using namespace std;

char preord[30],inord[30];

void recover(int preleft,int preright,int inleft,int inright)
{
	int root,leftsize,rightsize;
	
	assert(preleft<=preright && inleft<=inright);//条件不满足时，结束函数
	for(root=inleft;root<=inright;root++)
		if(preord[preleft]==inord[root]) break;
		leftsize =root-inleft;
		rightsize=inright-root;
		if(leftsize>0)
			recover(preleft+1,preleft+leftsize,inleft,root-1);
		if(rightsize>0)
			recover(preleft+leftsize+1,preright,root+1,inright);
		cout<<inord[root];
}
void solve_case()
{
	int n=strlen(preord);
	recover(0,n-1,0,n-1);
	cout<<endl;
}
int main()
{
	while(cin>>preord>>inord)
		solve_case();
	return 0;
}