[uva] Add C++ solution for 11770 - Lighting Away.

Author: abeaumont

uva/11770-1.ans

@@ -0,0 +1,2 @@
+Case 1: 2
+Case 2: 2

uva/11770-1.in

@@ -0,0 +1,13 @@
+2
+5 4
+1 2
+1 3
+3 4
+5 3
+
+4 4
+1 2
+1 3
+4 2
+4 3
+

uva/11770.cc

@@ -0,0 +1,55 @@
+// https://uva.onlinejudge.org/external/117/11770.pdf
+#include<bits/stdc++.h>
+using namespace std;
+using vi=vector<int>;
+using vvi=vector<vi>;
+using qi=queue<int>;
+int main(){
+  ios::sync_with_stdio(0);
+  cin.tie(0);
+  int t,n,m,u,v;
+  cin>>t;
+  for(int T=1;T<=t;T++){
+    cin>>n>>m;
+    vvi g(n),h(n),c;
+    for(int i=0;i<m;i++){
+      cin>>u>>v;
+      u--;v--;
+      g[u].push_back(v);
+      h[v].push_back(u);
+    }
+    vi a,s(n),t(n),r(n);
+    function<void(int)>dfs1=[&](int i){
+      s[i]=1;
+      for(int j:g[i])
+        if(!s[j])dfs1(j);
+      a.push_back(i);
+    };
+    for(int i=0;i<n;i++)
+      if(!s[i])dfs1(i);
+    reverse(a.begin(),a.end());
+    function<void(int)>dfs2=[&](int i){
+      t[i]=1;
+      c.back().push_back(i);
+      for(int j:h[i])
+        if(!t[j])dfs2(j);
+    };
+    for(int i=0;i<a.size();i++)
+      if(!t[a[i]]){
+        c.push_back(vi());
+        dfs2(a[i]);
+      }
+    function<void(int)>dfs3=[&](int i){
+      r[i]=1;
+      for(int j:g[i])
+        if(!r[j])dfs3(j);
+    };
+    int k=0;
+    for(vi &x:c)
+      if(!r[x[0]]){
+        k++;
+        dfs3(x[0]);
+      }
+    cout<<"Case "<<T<<": "<<k<<"\n";
+  }
+}

uva/README.md

@@ -121,6 +121,8 @@ There are solutions for the following
    ([problem site](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2726))
 1. [11690 - Money Matters](11690.cc)
    ([problem site](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2737))
+1. [11770 - Lighting Away](11770.cc)
+   ([problem site](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=24&page=show_problem&problem=2870))
 1. [11838 - Come and Go](11838.cc)
    ([problem site](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=24&problem=2938))
 1. [11966 - Galactic Bonding](11966.cc)