Snakes and ladders submission

Author: andrewyang96

Graph Theory/Snakes and Ladders/andrew.py

@@ -0,0 +1,74 @@
+class VisitTracker(object):
+    def __init__(self, n):
+        self.n = n
+        self.l = [False,]*n
+    def visited(self, i):
+        if i <= 0 or i > self.n:
+            raise ValueError("i is out-of-bounds")
+        return self.l[i-1]
+    def setVisited(self, i):
+        if i <= 0 or i > self.n:
+            raise ValueError("i is out-of-bounds")
+        self.l[i-1] = True
+
+class Board(object):
+    def __init__(self, ladders, snakes, maxNum=100):
+        self.jumps = {}
+        # validate ladders
+        for a,b in ladders:
+            if a >= b:
+                raise ValueError("Ladders must move up")
+            if a in self.jumps:
+                raise ValueError("Redefinition of a jump")
+            if b in self.jumps:
+                raise ValueError("Cannot chain jumps")
+            self.jumps[a] = b
+        # validate snakes
+        for a,b in snakes:
+            if a <= b:
+                raise ValueError("Snakes must move down")
+            if a in self.jumps:
+                raise ValueError("Redefinition of a jump")
+            if b in self.jumps:
+                raise ValueError("Cannot chain jumps")
+            self.jumps[a] = b
+        self.maxNum = 100
+    def nextNums(self, currNum):
+        nextNs = [currNum+die for die in xrange(1,7)]
+        for idx, num in enumerate(nextNs[:]):
+            if num > self.maxNum: # prevent overflow
+                nextNs[idx] = currNum
+            elif num in self.jumps: # ladders or snakes
+                nextNs[idx] = self.jumps[num]
+        return nextNs
+    def solve(self):
+        q = [(1,0),]
+        v = VisitTracker(self.maxNum)
+        while len(q) > 0:
+            currNum, depth = q.pop(0)
+            if currNum == self.maxNum:
+                return depth
+            elif not v.visited(currNum):
+                v.setVisited(currNum)
+                for num in self.nextNums(currNum):
+                    q.append((num, depth+1))
+        return -1
+            
+
+def getInputs():
+    numTestcases = input()
+    testcases = []
+    for t in xrange(numTestcases):
+        ladders = []
+        for n in xrange(input()):
+            ladders.append([int(i) for i in raw_input().split(" ")])
+        snakes = []
+        for m in xrange(input()):
+            snakes.append([int(i) for i in raw_input().split(" ")])
+        testcases.append(Board(ladders, snakes))
+    return testcases
+
+if __name__ == "__main__":
+    testcases = getInputs()
+    for testcase in testcases:
+        print testcase.solve()