554.Brick Wall

554.Brick Wall

• 题目描述：There is a brick wall in front of you. The wall is rectangular and has several rows of bricks. The bricks have the same height but different width. You want to draw a vertical line from the top to the bottom and cross the least bricks.

  The brick wall is represented by a list of rows. Each row is a list of integers representing the width of each brick in this row from left to right.

  If your line go through the edge of a brick, then the brick is not considered as crossed. You need to find out how to draw the line to cross the least bricks and return the number of crossed bricks.

  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.

• Example:

  Input: 
  [[1,2,2,1],
  [3,1,2],
  [1,3,2],
  [2,4],
  [3,1,2],
  [1,3,1,1]]
  Output: 2

• 题目大意：你面前有一堵砖墙。 墙是长方形的，有几排砖。 砖具有相同的高度，但宽度不同。 你想从上到下画一条垂直线，并穿过最少的砖块。

• 思路：HashMap

• 代码

  package HashTable;
  
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  /**
  * @author OovEver
  * 2018/1/14 17:35
  */
  class Solution {
  public int leastBricks(List> wall) {
          Map map = new HashMap<>();
      for (List row : wall) {
          int sum = 0;
          for(int i=0;i1;i++) {
              sum += row.get(i);
              map.put(sum, map.getOrDefault(sum, 0) + 1);
          }
      }
    int res = wall.size();
      for (int key : map.keySet()) {
          res = Math.min(wall.size() - map.get(key), res);
      }
      return res;  
  }
  }