Task 15.1, 16.1, 16.2. Naive solution for 15.2, should use A*

15/15.py

@@ -0,0 +1,81 @@
+from timeit import timeit as _timeit
+timeit = lambda x: _timeit(x, globals=globals(), number=1)
+from collections import defaultdict
+
+def find_min_risk(field):
+    M = len(field[0])
+    N = len(field)
+    field = defaultdict(lambda: float("+inf"), {(i,j): int(x) for i, line in enumerate(field) for j,x in enumerate(line)})
+    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
+    stack = []
+    def f(i, j, s):
+        stack.append((i,j,s))
+        if d[(i,j)] <= s:
+            return
+        d[(i,j)] = s
+        if (i, j) == (N-1, M-1):
+            return
+        for di, dj in directions:
+            f(i+di, j+dj, s+field[(i,j)])
+    d = defaultdict(lambda: float("+inf"))
+    f(0,0,0)
+    return d[(N-1, M-1)]
+
+def find_min_risk_opt1(field):
+    M = len(field[0])
+    N = len(field)
+    field = defaultdict(lambda: float("+inf"), {(i,j): int(x) for i, line in enumerate(field) for j,x in enumerate(line)})
+    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
+    stack = [(0,0,0)]
+    d = defaultdict(lambda: float("+inf"))
+    while stack:
+        i, j, s = stack.pop()
+        if d[(i,j)] <= s:
+            continue
+        d[(i,j)] = s
+        if (i, j) == (N-1, M-1):
+            continue
+        stack.extend([(i+di, j+dj, s+field[(i,j)]) for di, dj in directions][::-1])
+    return d[(N-1, M-1)]
+
+statement_field = """
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581
+""".strip().split('\n')
+print('a1:', timeit('assert find_min_risk(statement_field)==40'))
+print('b1:', timeit('assert find_min_risk_opt1(statement_field)==40'))
+
+statement_field = """
+1163751742
+1381373672
+2135511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944582
+""".strip().split('\n')
+x = int(statement_field[0][0])
+y = int(statement_field[-1][-1])
+print('a2:', timeit('assert find_min_risk(statement_field)-x+y==40'))
+print('b2:', timeit('assert find_min_risk_opt1(statement_field)-x+y==40'))
+
+with open("input") as f:
+    field = f.read().strip().split('\n')
+    
+x = int(field[0][0])
+y = int(field[-1][-1])
+print('b3:', timeit('print(find_min_risk_opt1(field)-x+y)'))
+
+
+