int binary_search(int* a, int low, int high, int goal) //二分查找 { while(low <= high) { int middle = (low+high)>>1; //(low+high)/2 if(a[middle] == goal) return middle; else if(a[middle] < goal) low = middle + 1; else high = middle - 1; } return -1; } void getNum(int *a, int len, int goal) { int i, index; for(i = 0; i < len-1; i++) { if(a[i] > a[i+1]) break; } if(a[i] >= goal) { index = binary_search(a, 0, i, goal); printf("%d\n",index); } if(a[i+1] <= goal) { index = binary_search(a+i+1, 0, len-i-2, goal); if(index != -1) index += (i+1); printf("%d\n",index); } }
#include "stdafx.h" #include<exception> int MinInOrder(int* numbers, int index1, int index2); int Min(int* numbers, int length) { if(numbers == NULL || length <= 0) throw new std::exception("Invalid parameters"); int index1 = 0; int index2 = length - 1; int indexMid = index1; while(numbers[index1] >= numbers[index2]) { // 如果index1和index2指向相邻的两个数, // 则index1指向第一个递增子数组的最后一个数字, // index2指向第二个子数组的第一个数字,也就是数组中的最小数字 if(index2 - index1 == 1) { indexMid = index2; break; } // 如果下标为index1、index2和indexMid指向的三个数字相等, // 则只能顺序查找 indexMid = (index1 + index2) / 2; if(numbers[index1] == numbers[index2] && numbers[indexMid] == numbers[index1]) return MinInOrder(numbers, index1, index2); // 缩小查找范围 if(numbers[indexMid] >= numbers[index1]) index1 = indexMid; else if(numbers[indexMid] <= numbers[index2]) index2 = indexMid; } return numbers[indexMid]; } int MinInOrder(int* numbers, int index1, int index2) { int result = numbers[index1]; for(int i = index1 + 1; i <= index2; ++i) { if(result > numbers[i]) result = numbers[i]; } return result; }
首先对前一半递增直接查找,找到即退出,后一半二分查找int binary_search(int *a,int low,int high,int goal) { while(low <= high) { int middle = (low+high)>>1; if(a[middle] == goal) return middle; else if(a[middle] > goal) high = middle-1; else low = middle + 1; } return -1; } void getnumber(int *a,int len ,int goal) { int i; for(i = 0 ; i < len ;i++) { if(a[i] == goal) { cout<<i; return; } if(a[i] > a[i+1]) break; } int low = i+1; int high = len-1; int num; if((num = binary_search(a,low,high,goal))>=0) cout<<num; else cout<<"no such data";
}