题目链接:https://leetcode-cn.com/problems/first-missing-positive/
题目描述
分析
1. 排序+循环
代码实现
public enum Q41 {
instance;
public int firstMissingPositive(int[] nums) {
if(nums==null||nums.length==0)return 1;
// 排序
Arrays.sort(nums);
int l=nums.length;
// 都是负数 或 都是大于1的正数，直接返回1
if(nums[l-1]<=0||nums[0]>1){
return 1;
}
int minP=nums[l-1]+1;
for(int i=l-1;i>0;i--){
int num=nums[i];
int last=nums[i-1];
if(num>=0&&last>=0){
// 若前后两个数相等或是连续，则跳过
if(num==last||num==last+1){
continue;
}
minP=last+1;
}else if(last<1&&num>1){
return 1;
}
}
return minP;
}
public static void main(String[] args) {
// assert 3
System.out.println(Q41.instance.firstMissingPositive(new int[]{1,2,0}));
// assert 2
System.out.println(Q41.instance.firstMissingPositive(new int[]{3,4,-1,1}));
// assert 1
System.out.println(Q41.instance.firstMissingPositive(new int[]{7,8,9,11,12}));
// assert 3
System.out.println(Q41.instance.firstMissingPositive(new int[]{0,1,2,4,-1}));
}
}
Life is like an ocean.Only the one with resolute mind will reach the other shore. (Germany) Marx
生活就像海洋，只有意志坚强的任才能到达彼岸。– [德] 马克思
