LeetCode042接雨水

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题目:

给定 n 个非负整数表示每个宽度为 1 的柱子的高度图，计算按此排列的柱子，下雨之后能接多少雨水。

示例 1：

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编辑

• 输入：height = [0,1,0,2,1,0,1,3,2,1,2,1]
• 输出：6
• 解释：上面是由数组 [0,1,0,2,1,0,1,3,2,1,2,1] 表示的高度图，在这种情况下，可以接 6 个单位的雨水（蓝色部分表示雨水）。

示例 2：

• 输入：height = [4,2,0,3,2,5]
• 输出：9

java:

public class Leetcode042 {

    public static int trap(int[] height) {
        int sum = 0;
        for (int i = 0; i < height.length; i++) {
            if (i == 0 || i == height.length - 1) {
                continue;
            }
            //左高度.
            int left = height[i];
            //右高度.
            int right = height[i];
            for (int r = i + 1; r < height.length; r++) {
                if (height[r] > right) {
                    right = height[r];
                }
            }
            for (int l = i - 1; l >= 0; l--) {
                if (height[l] > left) {
                    left = height[l];
                }
            }
            int h = Math.min(left, right) - height[i];
            if (h > 0) {
                sum += h;
            }
        }
        return sum;
    }

    //单调栈
    public static int trap2(int[] height) {
        int size = height.length;
        if (size <= 2) {
            return 0;
        }

        Stack<Integer> stack = new Stack<>();
        stack.push(0);

        int sum = 0;
        for (int index = 1; index < size; index++) {
            Integer stackTop = stack.peek();
            if (height[index] < height[stackTop]) {
                stack.push(index);
            } else if (height[index] == height[stackTop]) {
                //相等的左边无法存水.
                stack.pop();
                stack.push(index);
            } else {
                int heightAtIdx = height[index];
                while (!stack.isEmpty() && (heightAtIdx > height[stackTop])) {
                    Integer mid = stack.pop();
                    if (!stack.isEmpty()) {
                        Integer left = stack.peek();
                        int h = Math.min(height[left], height[index]) - height[mid];
                        int w = index - left - 1;
                        int hold = h * w;
                        if (hold > 0){
                            sum += hold;
                        }
                         stackTop = stack.peek();
                    }
                }
                stack.push(index);
            }
        }
        return sum;
    }

    public static void main(String[] args) {
        int[] height1 = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1};
        int[] height2 = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1};
        System.out.println(trap2(height1));
        System.out.println(trap(height2));
    }
}

Go:

` package LeetCode

func Trap(nums []int) int { var left, right, leftMax, rightMax, result int right = len(nums) - 1 for left < right { if nums[left] < nums[right] { if nums[left] >= leftMax { leftMax = nums[left] } else { result += leftMax - nums[left] } left++ } else { if nums[right] > rightMax { rightMax = nums[right] } else { result += rightMax - nums[right] } right-- } } return result }

func Trap2(nums []int) int { if len(nums) <= 2 { return 0 } st := make([]int, 1, len(nums)) var res int for i := 1; i < len(nums); i++ { if nums[i] < nums[st[len(st)-1]] { st = append(st, i) } else if nums[i] == nums[st[len(st)-1]] { st = st[:len(st)-1] st = append(st, i) } else { for len(st) != 0 && nums[i] > nums[st[len(st)-1]] { top := st[len(st)-1] st = st[:len(st)-1] if len(st) != 0 { tmp := (min(nums[i], nums[st[len(st)-1]]) - nums[top]) * (i - st[len(st)-1] - 1) res += tmp } } st = append(st, i) } } return res }

func main() { array := []int{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1} trap := LeetCode.Trap(array) trap2 := LeetCode.Trap2(array) fmt.Println(trap) fmt.Println(trap2) }`

黯淡无光.

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