57 lines
1.9 KiB
C++
57 lines
1.9 KiB
C++
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// Source : https://leetcode.com/problems/island-perimeter/
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// Author : Hao Chen
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// Date : 2019-02-04
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/*****************************************************************************************************
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*
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* You are given a map in form of a two-dimensional integer grid where 1 represents land and 0
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* represents water.
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*
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* Grid cells are connected horizontally/vertically (not diagonally). The grid is completely
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* surrounded by water, and there is exactly one island (i.e., one or more connected land cells).
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*
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* The island doesn't have "lakes" (water inside that isn't connected to the water around the island).
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* One cell is a square with side length 1. The grid is rectangular, width and height don't exceed
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* 100. Determine the perimeter of the island.
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*
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* Example:
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*
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* Input:
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* [[0,1,0,0],
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* [1,1,1,0],
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* [0,1,0,0],
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* [1,1,0,0]]
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*
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* Output: 16
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*
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* Explanation: The perimeter is the 16 yellow stripes in the image below:
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*
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******************************************************************************************************/
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class Solution {
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public:
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int edge(vector<vector<int>> &grid, int x, int y) {
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int edge = 0;
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if (x==0 || (x>0 && grid[x-1][y] == 0 ) ) edge++; //up
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if (y==0 || (y>0 && grid[x][y-1] == 0 ) ) edge++; //left
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if (x == grid.size() - 1 ||
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(x < grid.size() - 1 && grid[x+1][y] == 0)) edge++; //down
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if (y == grid[0].size() - 1 ||
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(y < grid[0].size() - 1 && grid[x][y+1] == 0)) edge++; //right
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return edge;
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}
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int islandPerimeter(vector<vector<int>>& grid) {
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int perimeter = 0;
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for(int i=0; i<grid.size(); i++) {
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for(int j=0; j<grid[0].size(); j++) {
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if (grid[i][j] == 1) {
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perimeter += edge (grid, i, j);
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}
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}
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}
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return perimeter;
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}
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};
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