问题描述
给定一个字符串，要求对字符串中的字符按出现次数大小进行排序。题目链接：点我
样例输入输出
输入：s = “tree”
输出：”eert” 或 “eetr”
输入：s = “Aabb”
输出：”bbaA” 或 “bbAa”
问题解法
先统计每个字符出现的次数，然后对字符按次数进行排序，最后输出排序后的字符（按数量输出）。代码如下
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| class Solution {
public String frequencySort(String s) {
class Node {
int count;
char ch;
Node(char ch) {
this.ch = ch;
count = 0;
}
void increase() {
count++;
}
}
Node[] nodes = new Node[62];
for (int i = 0; i < 62; i++) {
if (i < 26) {
nodes[i] = new Node((char) ('a' + i));
} else if (i < 52) {
nodes[i] = new Node((char) ('A' + i - 26));
} else {
nodes[i] = new Node((char) ('0' + i - 52));
}
}
for (char ch : s.toCharArray()) {
int index;
if (ch >= 'a' && ch <= 'z') {
index = ch - 'a';
} else if (ch >= 'A' && ch <= 'Z') {
index = ch - 'A' + 26;
} else {
index = ch - '0' + 52;
}
nodes[index].increase();
}
Arrays.sort(nodes, (x, y) -> y.count - x.count);
StringBuilder sb = new StringBuilder();
for (Node node : nodes) {
for (int i = 0; i < node.count; i++) {
sb.append(node.ch);
}
}
return sb.toString();
}
}
|