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68 lines
2.6 KiB
Markdown
68 lines
2.6 KiB
Markdown
# [554. Brick Wall](https://leetcode.com/problems/brick-wall/)
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## 题目
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There is a rectangular brick wall in front of you with `n` rows of bricks. The `ith` row has some number of bricks each of the same height (i.e., one unit) but they can be of different widths. The total width of each row is the same.
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Draw a vertical line from the top to the bottom and cross the least bricks. If your line goes through the edge of a brick, then the brick is not considered as crossed. You cannot draw a line just along one of the two vertical edges of the wall, in which case the line will obviously cross no bricks.
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Given the 2D array `wall` that contains the information about the wall, return *the minimum number of crossed bricks after drawing such a vertical line*.
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**Example 1:**
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```
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Input: wall = [[1,2,2,1],[3,1,2],[1,3,2],[2,4],[3,1,2],[1,3,1,1]]
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Output: 2
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```
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**Example 2:**
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```
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Input: wall = [[1],[1],[1]]
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Output: 3
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```
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**Constraints:**
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- `n == wall.length`
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- `1 <= n <= 10^4`
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- `1 <= wall[i].length <= 10^4`
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- `1 <= sum(wall[i].length) <= 2 * 10^4`
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- `sum(wall[i])` is the same for each row `i`.
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- `1 <= wall[i][j] <= 2^31 - 1`
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## 题目大意
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你的面前有一堵矩形的、由 n 行砖块组成的砖墙。这些砖块高度相同（也就是一个单位高）但是宽度不同。每一行砖块的宽度之和应该相等。你现在要画一条 自顶向下 的、穿过 最少 砖块的垂线。如果你画的线只是从砖块的边缘经过，就不算穿过这块砖。你不能沿着墙的两个垂直边缘之一画线，这样显然是没有穿过一块砖的。给你一个二维数组 wall ，该数组包含这堵墙的相关信息。其中，wall[i] 是一个代表从左至右每块砖的宽度的数组。你需要找出怎样画才能使这条线 穿过的砖块数量最少 ，并且返回 穿过的砖块数量 。
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## 解题思路
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- 既然穿过砖块中缝不算穿过砖块，那么穿过最少砖块数量一定是穿过很多中缝。按行遍历每一行的砖块，累加每行砖块宽度，将每行砖块“缝”的坐标存在 map 中。最后取出 map 中出现频次最高的缝，即为铅垂线要穿过的地方。墙高减去缝出现的频次，剩下的即为穿过砖块的数量。
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## 代码
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```go
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package leetcode
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func leastBricks(wall [][]int) int {
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m := make(map[int]int)
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for _, row := range wall {
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sum := 0
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for i := 0; i < len(row)-1; i++ {
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sum += row[i]
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m[sum]++
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}
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}
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max := 0
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for _, v := range m {
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if v > max {
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max = v
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}
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}
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return len(wall) - max
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}
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``` |