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export default trap;function trap(height: number[]): number {    const n = height.length;    if (n == 0) {        return 0;    }
    const leftMax: number[] = new Array(n).fill(0);    leftMax[0] = height[0];    for (let i = 1; i < n; ++i) {        leftMax[i] = Math.max(leftMax[i - 1], height[i]);    }
    const rightMax: number[] = new Array(n).fill(0);    rightMax[n - 1] = height[n - 1];    for (let i = n - 2; i >= 0; --i) {        rightMax[i] = Math.max(rightMax[i + 1], height[i]);    }
    let ans = 0;    for (let i = 0; i < n; ++i) {        ans += Math.min(leftMax[i], rightMax[i]) - height[i];    }    return ans;}