题目
结果
代码
虽然通过了，但我这种算法太繁琐了，有空再看看题解怎么做的吧。
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| class Solution {
public boolean isPossible(int[] nums) {
Map<Integer, Integer> map = new HashMap<>();
for (int num : nums) {
map.put(num, map.getOrDefault(num, 0) + 1);
}
boolean[] flag = new boolean[nums.length];
int count = 0;
while (count != nums.length) {
Deque<Integer> stack = new LinkedList<>();
for (int i = 0; i < nums.length; i++) {
if (flag[i]) {
continue;
}
if (stack.isEmpty()) {
stack.push(nums[i]);
flag[i] = true;
count++;
continue;
}
if (nums[i] == stack.peek()) {
if (nums[i] == nums[nums.length - 1] || map.get(nums[i]) > map.get(nextNum(nums, i))) {
break;
}
} else {
if (nums[i] - 1 != stack.peek()) {
break;
}
stack.push(nums[i]);
flag[i] = true;
count++;
}
}
for (int num : stack) {
map.put(num, map.get(num) - 1);
}
if (!judge(stack)) {
return false;
}
}
return true;
}
private boolean judge(Deque<Integer> stack) {
if (stack.size() < 3) {
return false;
}
while (true) {
int tmp = stack.pop();
if (stack.isEmpty()) {
break;
}
if (tmp != stack.peek() + 1) {
return false;
}
}
return true;
}
private int nextNum(int[] nums, int index) {
for (int i = index + 1; i < nums.length; i++) {
if (nums[i] != nums[index]) {
return nums[i];
}
}
throw new RuntimeException("no way");
}
}
|
复杂度
时间复杂度：O（n²）
空间复杂度：O（n）