Leetcode

回味一下大一时候写的并查集，拿java写写看

class Solution {
    int[] f;
    public int findCircleNum(int[][] isConnected) {
        int n = isConnected.length;
        f = new int[n];
        for (int i = 0; i < n; i++) {
            f[i] = i;
        }
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if(isConnected[i][j] == 1) {
                    mix(i, j);
                }
            }
        }
        int ans = 0;
        for (int i = 0; i < n; i++) {
            if(find(i) == i) {
                ans ++;
            }
        }
        return ans;
    }
    void mix(int x, int y) {
        int fx = find(x);
        int fy = find(y);
        if(fx != fy) {
            f[fx] = fy;
        }
    }
    int find(int x) {
        while(x != f[x]) {
            x = f[x];
        }
        return x;
    }
}

简单优化

while(temp != x) {
   int next = f[temp];
   f[temp] = x;
   temp = next;
}

速度从3s变成1s