SHARE
TWEET

Untitled

a guest Feb 19th, 2019 54 Never
Not a member of Pastebin yet? Sign Up, it unlocks many cool features!
  1. import java.util.*;
  2.  
  3. class UF {
  4.  
  5.     private int[] parent;  // parent[i] = parent of i
  6.     private byte[] rank;   // rank[i] = rank of subtree rooted at i (never more than 31)
  7.     private int count;     // number of components
  8.  
  9.     /**
  10.      * Initializes an empty union–find data structure with {@code n} sites
  11.      * {@code 0} through {@code n-1}. Each site is initially in its own
  12.      * component.
  13.      *
  14.      * @param  n the number of sites
  15.      * @throws IllegalArgumentException if {@code n < 0}
  16.      */
  17.     public UF(int n) {
  18.         if (n < 0) throw new IllegalArgumentException();
  19.         count = n;
  20.         parent = new int[n];
  21.         rank = new byte[n];
  22.         for (int i = 0; i < n; i++) {
  23.             parent[i] = i;
  24.             rank[i] = 0;
  25.         }
  26.     }
  27.  
  28.     /**
  29.      * Returns the component identifier for the component containing site {@code p}.
  30.      *
  31.      * @param  p the integer representing one site
  32.      * @return the component identifier for the component containing site {@code p}
  33.      * @throws IllegalArgumentException unless {@code 0 <= p < n}
  34.      */
  35.     public int find(int p) {
  36.         validate(p);
  37.         while (p != parent[p]) {
  38.             parent[p] = parent[parent[p]];    // path compression by halving
  39.             p = parent[p];
  40.         }
  41.         return p;
  42.     }
  43.  
  44.     /**
  45.      * Returns the number of components.
  46.      *
  47.      * @return the number of components (between {@code 1} and {@code n})
  48.      */
  49.     public int count() {
  50.         return count;
  51.     }
  52.  
  53.     /**
  54.      * Returns true if the the two sites are in the same component.
  55.      *
  56.      * @param  p the integer representing one site
  57.      * @param  q the integer representing the other site
  58.      * @return {@code true} if the two sites {@code p} and {@code q} are in the same component;
  59.      *         {@code false} otherwise
  60.      * @throws IllegalArgumentException unless
  61.      *         both {@code 0 <= p < n} and {@code 0 <= q < n}
  62.      */
  63.     public boolean connected(int p, int q) {
  64.         return find(p) == find(q);
  65.     }
  66.  
  67.     /**
  68.      * Merges the component containing site {@code p} with the
  69.      * the component containing site {@code q}.
  70.      *
  71.      * @param  p the integer representing one site
  72.      * @param  q the integer representing the other site
  73.      * @throws IllegalArgumentException unless
  74.      *         both {@code 0 <= p < n} and {@code 0 <= q < n}
  75.      */
  76.     public void union(int p, int q) {
  77.         int rootP = find(p);
  78.         int rootQ = find(q);
  79.         if (rootP == rootQ) return;
  80.  
  81.         // make root of smaller rank point to root of larger rank
  82.         if      (rank[rootP] < rank[rootQ]) parent[rootP] = rootQ;
  83.         else if (rank[rootP] > rank[rootQ]) parent[rootQ] = rootP;
  84.         else {
  85.             parent[rootQ] = rootP;
  86.             rank[rootP]++;
  87.         }
  88.         count--;
  89.     }
  90.  
  91.     // validate that p is a valid index
  92.     private void validate(int p) {
  93.         int n = parent.length;
  94.         if (p < 0 || p >= n) {
  95.             throw new IllegalArgumentException("index " + p + " is not between 0 and " + (n-1));  
  96.         }
  97.     }
  98.  
  99. }
RAW Paste Data
We use cookies for various purposes including analytics. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy. OK, I Understand
 
Top