Tree UVA - 548 (DFS+建立二叉树)

解题思路:

根据中序后序建立二叉树,利用DFS便利每条路径的和

这里要注意输入:

bool read_List(int* a){
	string line; 
	if(!getline(cin,line)) return false;  //如果为空,则直接退出
	stringstream ss(line);  //化为stream流
	int x;
	n = 0;
	while(ss >> x) a[n++] = x;
	return n > 0;
}

我们可以在读入字符串后,利用stringstream去除空格,把字符串中的数字全部读出来

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int MAXN = 10010;
int midArr[MAXN],postArr[MAXN];  
int n;
int leastNode = 0x3fffffff;
int minRoute = 0x3fffffff;
vector routes;
bool flag = true;
bool read_List(int* a){
	string line; 
	if(!getline(cin,line)) return false;  //如果为空,则直接退出
	stringstream ss(line);  //化为stream流
	int x;
	n = 0;
	while(ss >> x) a[n++] = x;
	return n > 0;
}
struct stNode{
	int stData;
	stNode *lchild,*rchild;
	stNode(int _value){
		stData = _value;
		lchild = rchild = nullptr;
	}
};
//DFSfind
void DFSfind(stNode* sroot){
	if(sroot->lchild == nullptr && sroot->rchild == nullptr){
		routes.push_back(sroot->stData);
		//求和
		int tempSum = 0;
		for(int k = 0; k < routes.size();++k){
			tempSum += routes[k];  //加上tempSum的和
		}
		if(tempSum == minRoute){
		   if(sroot->stData < leastNode){
			   leastNode = sroot->stData;
		   }
		}
		else if(tempSum < minRoute){
			minRoute = tempSum;
			leastNode = sroot->stData;
		}
		routes.pop_back();
	}
	if(sroot->lchild != nullptr){
		routes.push_back(sroot->stData);
		DFSfind(sroot->lchild);
		routes.pop_back();  //出队
	}
	if(sroot->rchild != nullptr){
		routes.push_back(sroot->stData);
		DFSfind(sroot->rchild);
		routes.pop_back();
	}
}

stNode* buildTree(int posL,int posR,int inL,int inR){
	if(posL > posR) return nullptr;  
	int curposRoot = postArr[posR];
	int curInroot = -1;
	int k;
	for(int i = inL;i <= inR;++i){
	    if(midArr[i] == curposRoot){
			curInroot = midArr[i];
			k = i;
			break;
		}
	}
	if(curInroot == -1) return nullptr;
	stNode* croot = new stNode(curposRoot);  
	int numK = k - inL;
	
	croot->lchild = buildTree(posL,posL+numK-1,inL,k-1);  //向左
	croot->rchild = buildTree(posL+numK,posR-1,k+1,inR);  //向右
	return croot;  //返回头结点
}

int main(){
	while(read_List(midArr)){
		read_List(postArr);
		leastNode = 0x3fffffff;
        minRoute = 0x3fffffff;
		routes.clear();
		stNode* troot = buildTree(0,n-1,0,n-1);  //建树
		DFSfind(troot);
		cout<