Solved problem 10777 - God! Save me from UVA

Author: AliOsm

UVA/10777 - God! Save me.cpp

@@ -0,0 +1,59 @@
+/*
+  Idea:
+    - We can solve this problem using DP.
+    - In each step in the DP try to take each door using its prbability.
+    - If the door takes you outside, then add its hours * its probability
+      to the result, otherwise if the door bring you back add its hours *
+      its probability and go from it to new recursion call, but the multiply
+      the returned value with the current door probability.
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int const N = 1e2 + 1;
+int t, n, x[N];
+double p[N], dp[N * N];
+
+double rec(int cur) {
+  if(cur > N * N)
+    return 0;
+
+  double &ret = dp[cur];
+  if(ret == ret)
+    return ret;
+  ret = 0;
+
+  for(int i = 0; i < n; ++i)
+    if(x[i] > 0)
+      ret += 1.0 * x[i] * p[i];
+    else {
+      ret += 1.0 * -x[i] * p[i] + p[i] * rec(cur + 1);
+    }
+
+  return ret;
+}
+
+int main() {
+  int kase = 0;
+  scanf("%d", &t);
+  while(t-- != 0) {
+    memset(dp, -1, sizeof dp);
+
+    bool ok = false;
+    scanf("%d", &n);
+    for(int i = 0; i < n; ++i) {
+      scanf("%d %lf", x + i, p + i);
+      if(x[i] > 0)
+        ok = true;
+    }
+
+    if(!ok)
+      printf("Case %d: God! Save me\n", ++kase);
+    else
+      printf("Case %d: %.2lf\n", ++kase, rec(0));
+  }
+
+  return 0;
+}

UVA/README.md

@@ -118,6 +118,7 @@
 - [10721 - Bar Codes](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1662)
 - [10731 - Test](https://uva.onlinejudge.org/index.php?option=onlinejudge&Itemid=99999999&page=show_problem&problem=1672)
 - [10765 - Doves and bombs](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1706)
+- [10777 - God! Save me](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1718)
 - [10789 - Prime Frequency](https://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1730)
 - [10804 - Gopher Strategy](https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1745)
 - [10815 - Andy's First Dictionary](https://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1756)