leetcode 463. Island Perimeter（C语言，二维数组，周长）23

以下为原创，如有错误，还望指出

贴原题：

You are given a map in form of a two-dimensional integer grid where 1
represents land and 0 represents water. Grid cells are connected
horizontally/vertically (not diagonally). The grid is completely
surrounded by water, and there is exactly one island (i.e., one or
more connected land cells). The island doesn’t have “lakes” (water
inside that isn’t connected to the water around the island). One cell
is a square with side length 1. The grid is rectangular, width and
height don’t exceed 100. Determine the perimeter of the island.

Example:

[[0,1,0,0], [1,1,1,0], [0,1,0,0], [1,1,0,0]]

Answer: 16 Explanation: The perimeter is the 16 yellow stripes in the
image below:

解析：
　　本题就是要求二维数组中为１的元素组成图形的周长，那么我们只需要算出——１的个数*４减去相邻为１的个数即可。

　　我在写的时候，把gridRowSize理解成了每一行中元素的个数，把gridColSize当成了每一列中元素的个数，导致这种错误提示——“Line 7: load of misaligned address 0x000000000021 for type ‘int’, which requires 4 byte alignment”。
　　但其实gridRowSize是行数，gridColSize是列数。引以为戒。

Ｃ代码：

int islandPerimeter(int** grid, int gridRowSize, int gridColSize) {
    int num=0;
    for(int i=0; ifor(int j=0; jif(grid[i][j])//该位置为1
            {
                num+=4;//个数*4
                if(i && grid[i-1][j])//相邻为1则减1
                {
                    num--;
                }
                if(i1 && grid[i+1][j])
                {
                    num--;
                }
                if(j && grid[i][j-1])
                {
                    num--;
                }
                if(j1 && grid[i][j+1])
                {
                    num--;
                }
            }
        }
    }
    return num;
}