Task · algorithms medium Python ·
Trapping rain water
The list gives the heights of bars of width 1 standing side by side. After rain, water collects between the bars. Return the total units of trapped water. Up to 500,000 bars.
Signature
def trap(heights: list[int]) -> int:Examples
trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1]) # -> 6
trap([4, 2, 0, 3, 2, 5]) # -> 9Plus 7 hidden tests and 1 large-input test under a time limit; their inputs are not shown. Tasks are given to the models in English.
#1SpaceXAI Grok Build 0.1solved · 10 of 10 testsanswer in 8.7 s · runtime 201 ms · $0.0032 ✓ trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1])expected 6 <1 ms ✓ trap([4, 2, 0, 3, 2, 5])expected 9 <1 ms ✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ 1 ms✓ <1 ms⏱ 194 msCode
def trap(heights: list[int]) -> int: if not heights: return 0 left, right = 0, len(heights) - 1 left_max = right_max = 0 res = 0 while left < right: if heights[left] < heights[right]: if heights[left] >= left_max: left_max = heights[left] else: res += left_max - heights[left] left += 1 else: if heights[right] >= right_max: right_max = heights[right] else: res += right_max - heights[right] right -= 1 return res#1Qwen3.8 Max (0902)solved · 10 of 10 testsanswer in 7.1 s · runtime 217 ms · $0.0025 ✓ trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1])expected 6 3 ms ✓ trap([4, 2, 0, 3, 2, 5])expected 9 <1 ms ✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms⏱ 209 msCode
def trap(heights: list[int]) -> int: if not heights: return 0 left, right = 0, len(heights) - 1 left_max = right_max = 0 water = 0 while left < right: if heights[left] < heights[right]: if heights[left] >= left_max: left_max = heights[left] else: water += left_max - heights[left] left += 1 else: if heights[right] >= right_max: right_max = heights[right] else: water += right_max - heights[right] right -= 1 return water#1MoonshotAI Kimi K2.7 Codesolved · 10 of 10 testsanswer in 6.7 s · runtime 220 ms · $0.0012 ✓ trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1])expected 6 <1 ms ✓ trap([4, 2, 0, 3, 2, 5])expected 9 <1 ms ✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms✓ <1 ms⏱ 214 msCode
def trap(heights: list[int]) -> int: left, right = 0, len(heights) - 1 left_max, right_max = 0, 0 water = 0 while left < right: if heights[left] < heights[right]: if heights[left] >= left_max: left_max = heights[left] else: water += left_max - heights[left] left += 1 else: if heights[right] >= right_max: right_max = heights[right] else: water += right_max - heights[right] right -= 1 return water#1Google Gemini 4 Argonsolved · 10 of 10 testsanswer in 16 s · runtime 236 ms · $0.0017 ✓ trap([0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1])expected 6 <1 ms ✓ trap([4, 2, 0, 3, 2, 5])expected 9 <1 ms ✓ <1 ms✓ <1 ms✓ 1 ms✓ <1 ms✓ 1 ms✓ 2 ms✓ 3 ms⏱ 224 msCode
from itertools import accumulate def trap(heights: list[int]) -> int: if len(heights) < 3: return 0 max_h = max(heights) idx = heights.index(max_h) return ( sum(accumulate(heights[:idx], max)) + sum(accumulate(heights[:idx:-1], max)) - sum(heights) + max_h )
Tokens cost: $0.0086 · How rounds are run and scored →