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- You are given a string s, and an array of pairs of indices in the string pairs where pairs[i] = [a, b] indicates 2 indices(0-indexed) of the string.
- You can swap the characters at any pair of indices in the given pairs any number of times.
- Return the lexicographically smallest string that s can be changed to after using the swaps.
-
- Example 1:
- Input: s = "dcab", pairs = [[0,3],[1,2]]
- Output: "bacd"
- Explaination:
- Swap s[0] and s[3], s = "bcad"
- Swap s[1] and s[2], s = "bacd"
- Example 2:
- Input: s = "dcab", pairs = [[0,3],[1,2],[0,2]]
- Output: "abcd"
- Explaination:
- Swap s[0] and s[3], s = "bcad"
- Swap s[0] and s[2], s = "acbd"
- Swap s[1] and s[2], s = "abcd"
- Example 3:
- Input: s = "cba", pairs = [[0,1],[1,2]]
- Output: "abc"
- Explaination:
- Swap s[0] and s[1], s = "bca"
- Swap s[1] and s[2], s = "bac"
- Swap s[0] and s[1], s = "abc"
-
- Constraints:
- 1 <= s.length <= 10^5
- 0 <= pairs.length <= 10^5
- 0 <= pairs[i][0], pairs[i][1] < s.length
- s only contains lower case English letters.
复制代码
- class Solution {
- public String smallestStringWithSwaps(String s, List<List<Integer>> pairs) {
- int len = s.length();
- UnionFind u = new UnionFind(len);
- for(List <Integer> list: pairs){
- u.union(list.get(0),list.get(1));
- }
-
- Map <Integer, List<Character>> map = new HashMap<>();
- for(int i = 0; i <len; i++){
- int head = u.find(i);
- List<Character> cha = map.computeIfAbsent(head, k -> new ArrayList<>());
- cha.add(s.charAt(i));
- }
-
- for(List<Character> c : map.values()){
- Collections.sort(c);
- }
-
- StringBuilder re = new StringBuilder();
- Map <Integer,Integer> help = new HashMap<>();
- for(int i = 0 ; i< len; i++){
-
- int x =u.find(i);
- List<Character> list = map.get(x);
- help.put(x, help.getOrDefault(x,-1)+1);
- char aa = list.get(help.get(x));
- re.append(aa);
- }
- return re.toString();
- }
-
- public class UnionFind{
-
- int[] parent;
- int[] size;
-
- public UnionFind(int x){
- parent = new int[x];
- size = new int[x];
- for(int i = 0; i < x ; i++){
- size[i] = 1;
- parent[i] = i;
- }
-
- }
-
- public int find(int x){
- int root = x;
- while(root != parent[root]){
-
- parent[root] = parent[parent[root]];
- root = parent[root];
- }
- return root;
- }
-
- public int union(int x, int y){
- int rootx = find(x);
- int rooty = find(y);
-
- if(rootx == rooty){
- return size[rootx];
- }
-
- if(size[rootx] > size[rooty]){
- parent[rooty] = rootx;
- size[rootx] = size[rootx] + size[rooty];
- return size[rootx];
- }
- else if(size[rootx] < size[rooty]){
- parent[rootx] = rooty;
- size[rooty] = size[rooty] + size[rootx];
- return size[rooty];
- }
- else{
- parent[rootx] = rooty;
- size[rooty] = size[rooty] + size[rootx];
- return size[rooty];
- }
- }
- }
- }
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