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package byteDance;

/**

* Created by lizeyang on 2020/5/13.

* 接雨水: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。

*/

public class test19 {

public static int test(int[] nums) {

//时间复杂度O(n)

if (nums == null || nums.length <= 1) {

return 0;

}

int area = 0;

int max = nums[0], maxIndex = 0;

//找到最高处和下标

for (int i = 0; i < nums.length; i++) {

if (nums[i] > max) {

max = nums[i];

maxIndex = i;

}

}

//从左边依次走到最高处，如果左边大于右边，可以接雨水

int tmp = nums[0];

for (int i = 1; i < maxIndex; i++) {

if (nums[i] < tmp) {

area += tmp - nums[i];

} else {

tmp = nums[i];

}

}

//从右边依次走到最高处，如果右边大于左边，可以接雨水

tmp = nums[nums.length - 1];

for (int i = nums.length - 2; i > maxIndex; i--) {

if (nums[i] > tmp) {

tmp = nums[i];

} else {

area += tmp - nums[i];

}

}

return area;

}

public static void main(String[] args) {

int[] nums = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1};

System.out.println(test(nums));

}

}