算法（Algorithms）第4版 练习 1.5.16

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFQuickFind {

private int[] id;//access to component id (site indexed)
private int count;//number of components

private static int cost = 0;//for plot

public UFQuickFind(int n) {
//initialize count and id
count = n;

id = new int
;
for(int i = 0; i < n; i++) {
id[i] = i;
}

}

public int count() {
return count;
}

public boolean connected(int p, int q) {
return find(p) == find(q);
}

public int find(int p) {
cost++;//for plot
return id[p];
}

public void union(int p, int q) {

int pID = find(p);
int qID = find(q);

//do nothing if p and q are already
//in the same component
if(pID == qID)
return;

//rename p's component to q's name
for(int i = 0; i < id.length; i++) {
if(id[i] == pID) {
id[i] = qID;
cost++;//for plot
}
cost++;//for plot
}
count--;

}

@Override
public String toString() {
String s = "";

for(int i = 0; i < id.length; i++) {
s += id[i] + " ";
}
s += "\n" + count + " components";

return s;
}

//for plot
private static void initStdDraw() {
StdDraw.setXscale(0, 900);
StdDraw.setYscale(0, 1300);
StdDraw.setPenRadius(0.002);
StdDraw.textLeft(1, 625, "625");
}

//for plot
private static void plot(int i, int cost, int totalcost) {

double average = (totalcost * 1.0) / i;

StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.point(i, cost);
StdDraw.setPenColor(StdDraw.RED);
StdDraw.point(i, average);
}

public static void main(String[] args) {

//initialize N components
int N = StdIn.readInt();
UFQuickFind uf = new UFQuickFind(N);
//        StdOut.println(uf);

//total cost for plot
int totalcost = 0;
int i = 0;//ith connection processed
initStdDraw();

while(!StdIn.isEmpty()) {

cost = 0;//initialize for every inputs pair, for plot

int p = StdIn.readInt();
int q = StdIn.readInt();

if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");

totalcost += cost;//compute total cost, for plot
i++;
plot(i, cost, totalcost);

continue;
}

uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);

totalcost += cost;//compute total cost, for plot
i++;
plot(i,cost,totalcost);
}

}

}

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFQuickUnion {

private int[] id;//save the site's parent link(site indexed)
private int count;//number of components

private static int cost = 0;//for plot

public UFQuickUnion(int n) {

count = n;

id = new int
;
for(int i = 0; i < n; i++)
id[i] = i;

}

public int count() {
return count;
}

public boolean connected(int p, int q) {
return find(p) == find(q);
}

public int find(int p) {

//find root
//id[p] save the parent of p
while(p != id[p]) {
p = id[p];
cost += 2;//for plot
}
cost++;//for plot

return p;
}

public void union(int p, int q) {

int pRoot = find(p);//find pRoot
int qRoot = find(q);//find qRoot

if(pRoot == qRoot)
return;

id[pRoot] = qRoot;
cost++;//for plot
count--;
}

@Override
public String toString() {
String s = "";

for(int i = 0; i < id.length; i++) {
s += id[i] + " ";
}
s += "\n" + count + " components";

return s;
}

//for plot
private static void initStdDraw() {
StdDraw.setXscale(0, 900);
StdDraw.setYscale(0, 1300);
StdDraw.setPenRadius(0.002);
StdDraw.textLeft(1, 650, "625");
}

//for plot
private static void plot(int i, int cost, int totalcost) {

double average = (totalcost * 1.0) / i;

StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.point(i, cost);
StdDraw.setPenColor(StdDraw.RED);
StdDraw.point(i, average);
}

public static void main(String[] args) {

//initialize N components
int N = StdIn.readInt();
UFQuickUnion uf = new UFQuickUnion(N);
//        StdOut.println(uf);

//total cost for plot
int totalcost = 0;
int i = 0;//ith connection processed
initStdDraw();

while(!StdIn.isEmpty()) {

cost = 0;//initialize for every inputs pair, for plot

int p = StdIn.readInt();
int q = StdIn.readInt();

if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");

totalcost += cost;//compute total cost, for plot
i++;
plot(i, cost, totalcost);

continue;
}

uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);

totalcost += cost;//compute total cost, for plot
i++;
plot(i, cost, totalcost);
}

}

}

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFWeightedQuickUnion {

private int[] id;//parent link(site indexed)
private int[] treesize;//size of component for roots(site indexed)
private int count;//number of components

private static int cost = 0;//for plot

public UFWeightedQuickUnion(int N) {

count = N;

id = new int
;
for(int i = 0; i < N; i++)
id[i] = i;

treesize = new int
;
for(int i = 0; i < N; i++)
treesize[i] = 1;

}

public int count() {
return count;
}

public boolean connected(int p, int q) {
return find(p) == find(q);
}

public int find(int p) {

while(p != id[p]) {
p = id[p];
cost += 2;//for plot
}
cost++;//for plot

return p;

}

public void union(int p, int q) {

int pRoot = find(p);
int qRoot = find(q);

if(pRoot == qRoot)
return;

//make smaller root point to larger one
if(treesize[pRoot] < treesize[qRoot]) {
id[pRoot] = qRoot;
treesize[qRoot] += treesize[pRoot];
cost += 5;//for plot
} else {
id[qRoot] = pRoot;
treesize[pRoot] += treesize[qRoot];
cost += 5;//for plot
}

count--;

}

@Override
public String toString() {
String s = "";

for(int i = 0; i < id.length; i++) {
s += id[i] + " ";
}
s += "\n";

for(int i = 0; i < treesize.length; i++) {
s += treesize[i] + " ";
}
s += "\n" + count + " components";

return s;
}

//for plot
private static void initStdDraw() {
StdDraw.setXscale(0, 900);
StdDraw.setYscale(0, 1300);
StdDraw.setPenRadius(0.002);
StdDraw.textLeft(1, 625, "625");
}

//for plot
private static void plot(int i, int cost, int totalcost) {

double average = (totalcost * 1.0) / i;

StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.point(i, cost);
StdDraw.setPenColor(StdDraw.RED);
StdDraw.point(i, average);
}

public static void main(String[] args) {

//initialize N components
int N = StdIn.readInt();
UFWeightedQuickUnion uf = new UFWeightedQuickUnion(N);
//        StdOut.println(uf);

//total cost for plot
int totalcost = 0;
int i = 0;//ith connection processed
initStdDraw();

while(!StdIn.isEmpty()) {

cost = 0;//initialize for every inputs pair, for plot

int p = StdIn.readInt();
int q = StdIn.readInt();

if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");

totalcost += cost;//compute total cost, for plot
i++;
plot(i, cost, totalcost);

continue;
}

uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);

totalcost += cost;//compute total cost, for plot
i++;
plot(i, cost, totalcost);
}

}

}