Solved problem 1097 - Code the Tree from ZOJ

Author: AliOsm

ZOJ/1097 - Code the Tree.cpp

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+/*
+  Idea:
+    - Using recursion we can build the tree from the input.
+    - When the tree is ready to use we can use priority queue
+      to track the leaf nodes.
+    - Each time we remove a node from the tree we can remove it
+      from the `vector` of the parent node.
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+char s[10001];
+int n, len;
+vector<int> sol;
+vector<vector<int> > g;
+priority_queue<int> pq;
+
+int getInt(int idx) {
+  int ret = 0;
+  while(isdigit(s[idx]))
+    ret *= 10, ret += (s[idx++] - '0');
+  return ret;
+}
+
+void build(int idx, int par) {
+  int cur = getInt(idx);
+  n = max(n, cur);
+  
+  if(par != -1)
+    g[par].push_back(cur),
+    g[cur].push_back(par);
+
+  for(int i = idx, cnt = 1; i < len; ++i) {
+    cnt += s[i] == '(';
+    cnt -= s[i] == ')';
+    if(cnt == 0)
+      break;
+    if(s[i] == '(' && cnt == 2)
+      build(i + 1, cur);
+  }
+}
+
+void rmv(int from, int target) {
+  for(int i = 0; i < g[from].size(); ++i)
+    if(g[from][i] == target) {
+      g[from].erase(g[from].begin() + i);
+      break;
+    }
+}
+
+int main() {
+  while(fgets(s, sizeof s, stdin)) {
+    n = 0;
+    len = strlen(s);
+    g.clear();
+    g.resize(1001);
+    build(1, -1);
+
+    for(int i = 1; i <= n; ++i)
+      if(g[i].size() == 1)
+        pq.push(-i);
+
+    sol.clear();
+    while(!pq.empty()) {
+      int top = -pq.top();
+      pq.pop();
+
+      sol.push_back(g[top][0]);
+      rmv(g[top][0], top);
+      if(g[g[top][0]].size() == 1)
+        pq.push(-g[top][0]);
+    }
+
+    for(int i = 0; i < int(sol.size()) - 1; ++i)
+      printf("%s%d", i == 0 ? "" : " ", sol[i]);
+    puts("");
+  }
+
+  return 0;
+}

ZOJ/README.md

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+# Problems
+
+- [1097 - Code the Tree](http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=97)