443. 压缩字符串

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class Solution {
public int compress(char[] chars) {
int n = chars.length;
int[] parent = new int[n];
for(int i = 0; i < n; i++){
parent[i] = i;
}

for(int i = 1; i < n; i++){
char ch = chars[i];
if(ch == chars[i-1]){
union(i, i-1, parent);
}
}

StringBuffer sb = new StringBuffer();
int count = 1;
sb.append(chars[0]);
for(int i = 1; i < n; i++){
int pre = find(i-1, parent);
int p1 = find(i, parent);
if(pre == p1){
count++;
}else{
if(count != 1){
sb.append(count +"");
count = 1;
}
sb.append(chars[i] +"");
}
}

if(count != 1){
sb.append(count +"");
count = 0;
}

for(int i = 0; i < sb.length(); i++){
chars[i] = sb.charAt(i);
}
return sb.length();
}

public int find(int k, int[] parent){
if(k != parent[k]){
parent[k] = find(parent[k], parent);
}
return parent[k];
}

public void union(int i, int j, int[] parent){
int x = find(i, parent);
int y = find(j, parent);
if(x != y){
parent[x] = y;
}
}
}