554. Brick Wall

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.

这道题主要是用map记录和的形式去解题，通过把每一行每一种和的个数数出来并且记录，最后取和次数出现最多的那个，再用总的层数去剪掉这个最大的和的出现次数，即可得解，这道题主要就是要理清解题思路就很容易了，
代码如下：

class Solution {public:    int leastBricks(vector<vector<int>>& wall) {        map<int,int>mail;        map<int,int>::iterator iter;        for(int i=0;i<wall.size();i++){            int sum=0;            for(int j=0;j<wall[i].size()-1;j++){                sum+=wall[i][j];                mail[sum]++;            }        }        int maxx=0;        for(iter=mail.begin();iter!=mail.end();iter++){            maxx=max(maxx,iter->second);        }        return wall.size()-maxx;    }};