QUESTION:
An array is monotonic if it is either monotone increasing or monotone decreasing.
An array A is monotone increasing if for all i <= j, A[i] <= A[j]. An array A is monotone decreasing if for all i <= j, A[i] >= A[j].
Return true if and only if the given array A is monotonic.
Example 1:
Input: [1,2,2,3]
Output: true
Example 2:
Input: [6,5,4,4]
Output: true
Example 3:
Input: [1,3,2]
Output: false
Example 4:
Input: [1,2,4,5]
Output: true
Example 5:
Input: [1,1,1]
Output: true
Note:
1 <= A.length <= 50000-100000 <= A[i] <= 100000
EXPLANATION:
首先我们可以考虑到数组具体是升序的还是降序的，还有平等的，所以boolean类型的值不太合适，选用int类型的值来表示升降序。
1.如果一直是升序，出现降序就直接返回false
2.如果一直是降序，出现升序就直接返回false
那么代码就出来了。
SOLUTION:
class Solution {
public boolean isMonotonic(int[] A) {
if(A.length<=0)return true;
int order = 0;
int pre = A[0];
for(int i = 1;i<A.length;i++){
int tmp = A[i];
if(tmp>pre && (order==0 || order == 1)){
order = 1;
pre = tmp;
continue;
}else if(tmp<pre && (order==0 || order==-1)){
order=-1;
pre=tmp;
continue;
}else if(tmp == pre){
pre=tmp;
continue;
}
return false;
}
return true;
}
}