Find Peak Element
2864 ワード
public class Solution {
public int findPeakElement(int[] num) {
// binary search http://siddontang.gitbooks.io/leetcode-solution/content/array/find_peak_element.html
if(num==null || num.length ==0) return -1;
if (num.length==1)
return 0;
int left=0, right=num.length-1;
int mid=left+(right-left)/2;
while(left<= right){
mid=left+(right-left)/2;
//if(mid == 0 || num[mid]>=num[mid-1] &&num[mid]>=num[mid+1] || mid == num.length-1 ) return mid;
// if((mid == 0 || num[mid]>=num[mid-1] ) && (num[mid]>=num[mid+1] || mid == num.length-1) ) return mid; // java index ， num[-1]
if((mid==0 && num[mid]>num[mid+1]) || (mid==num.length-1 && num[mid] > num[mid-1]) || ( num[mid]>num[mid+1] && num[mid] > num[mid-1])) return mid;
if(mid>0 && num[mid]<num[mid-1]){
right = mid-1;
}else
left = mid+1;
}
return mid;
}
}