又是满满的收获。stringstream，以及根据后序和中序遍历结果求树的方法。
1 #include <iostream> 2 #include <string> 3 #include <algorithm> 4 #include <cstring> 5 #include <cstdio> 6 #include <cmath> 7 #include <queue> 8 #include <set> 9 #include <map> 10 #include <list> 11 #include <stack> 12 #include <sstream> 13 #define mp make_pair 14 typedef long long ll; 15 typedef unsigned long long ull; 16 const int MAX=1e4+5; 17 const int INF=1e9+5; 18 using namespace std; 19 typedef pair<int,int> pii; 20 int in_order[MAX],post_order[MAX],lson[MAX],rson[MAX]; 21 int n; 22 bool read(int* a) 23 { 24 string line; 25 if(!getline(cin,line)) 26 return false; 27 stringstream ss(line); 28 n=0;int x; 29 while(ss>>x) 30 a[n++]=x; 31 return n>0; 32 } 33 int build(int L1,int R1,int L2,int R2) 34 { 35 if(L1>R1) 36 return 0; 37 int root=post_order[R2]; 38 int p=L1; 39 while(in_order[p]!=root) 40 ++p; 41 int cnt=p-L1; 42 lson[root]=build(L1,p-1,L2,L2+cnt-1); 43 rson[root]=build(p+1,R1,L2+cnt,R2-1); 44 return root; 45 } 46 int best,best_sum; 47 void dfs(int u,int sum) 48 { 49 sum+=u; 50 if(!lson[u]&&!rson[u]) 51 { 52 if(sum<best_sum||(sum==best_sum&&u<best)) 53 { 54 best=u;best_sum=sum; 55 } 56 } 57 if(lson[u]) 58 dfs(lson[u],sum); 59 if(rson[u]) 60 dfs(rson[u],sum); 61 } 62 int main() 63 { 64 while(read(in_order)) 65 { 66 memset(lson,0,sizeof(lson));memset(rson,0,sizeof(rson)); 67 read(post_order); 68 build(0,n-1,0,n-1); 69 best_sum=INF;best=INF; 70 dfs(post_order[n-1],0); 71 printf("%d ",best); 72 } 73 }