分治法
public static int Pro1_4_18(int[] a, int lo, int hi){ //[lo,hi)if(hi-lo<3) return 0;int mid = lo + (hi-lo)/2;if(a[mid-1]>a[mid]&&a[mid+1]>a[mid]) return mid;int Left = Pro1_4_18(a, lo, mid);if(Left!=0) return Left;int Right = Pro1_4_18(a, mid, hi);if(Right!=0) return Right;return 0;}