1function trap(heights) {
2 let water = 0;
3 for (let i = 0; i < heights.length; i++) {
4 const left = Math.max(...heights.slice(0, i + 1));
5 const right = Math.max(...heights.slice(i));
6 const level = Math.min(left, right);
7 if (level > heights[i]) water += level - heights[i];
8 }
9 return water;
10}