547. Number of Provinces

There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city c, then city a is connected indirectly with city c.

A province is a group of directly or indirectly connected cities and no other cities outside of the group.

You are given an n x n matrix isConnected where isConnected[i][j] = 1 if the ith city and the jth city are directly connected, and isConnected[i][j] = 0 otherwise.

Return the total number of provinces.

DFS搜索，当map[i][i] = 1时加入搜索。
搜索时将map[i][i]设为0。遍历并递归其数列。
当map[i][i]等于0时，返回。

class Solution {
    int[][] map;
    public int findCircleNum(int[][] isConnected) {
        map = isConnected;
        int count = 0;
        
        for(int i = 0; i < isConnected.length; i++){
            if(map[i][i] == 1){
                count++;
                dfs(i);
            }
        }
        return count;
    }
    
    private void dfs(int i){
        if(map[i][i] == 0){
            return;
        }
        map[i][i] = 0;
        for(int j = 0; j < map[0].length; j++){
            if(map[i][j] == 1){
                dfs(j);
            }
        }
    }
}