UVA 548 树

来源：互联网发布：产品设计建模软件编辑：程序博客网时间：2024/05/20 22:26

这道题的关键字在于根据中序遍历和后序遍历建立出二叉树。另外在寻找路径时，可使用深度优先的方式搜索，搜索到叶子节点时加以判断即可。
这里用到sstream来读入，也是一个技巧，记录下来。
代码如下：

#include<cstdio>#include<iostream>#include<algorithm>#include<cstring>#include<string>#include<sstream>using namespace std;const int maxn = 10005;const int root = 1;int Left[maxn], Right[maxn];int Value[maxn];int ins[maxn], pos[maxn];int n;int cnt;int bestSum = 1000000000;int best;bool getinput(int a[]){    string s;    if (!getline(cin,s))        return false;    stringstream ss(s);    n = 0;    int x;    while (ss >> x){        a[n++] = x;    }    return true;}void newTree(){    cnt = 0;    Left[root] = Right[root] = 0;    Value[root] = -1;}int newNode(){    ++cnt;    Left[cnt] = Right[cnt] = 0;    Value[cnt] = -1;    return cnt;}int build(int L1, int R1, int L2, int R2){    int t = 0;    if (L1 <= R1){        int v = pos[R2];        t = newNode();        Value[t] = v;        int i;        for (i = L1; i <= R1; i++){            if (ins[i] == v)                break;        }        int cnt = i - L1;        Left[t] = build(L1, i - 1, L2, L2+cnt-1);        Right[t] = build(i + 1, R1, L2 + cnt, R2-1);    }    return t;}void dfs(int p,int sum){    sum += Value[p];    if (!(Left[p] || Right[p])){        if (sum < bestSum || (sum == bestSum && Value[p] < best)){            best = Value[p];            bestSum = sum;        }    }    else{        if (Left[p])            dfs(Left[p], sum);        if (Right[p])            dfs(Right[p], sum);    }}int main(){    while (getinput(ins)){        getinput(pos);        newTree();        build(0, n-1, 0, n-1);        bestSum = 1000000000;        best = 10000;        dfs(root,0);        cout << best << endl;    }    return 0;}

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