二分查找

#include <stdio.h> int binarysearch(int a[], const int i, int n); int main(int argc, char** argv) { int a[20] = {1,2,3,4,5,6,7,8,9,10}; printf("%d", binarysearch(a, 5, 10)); } int binarysearch(int a[], const int x, int n) { int left = 0; int right = n - 1; int middle = 0; while(left <= right) { middle = (left + right) / 2; if (x == a[middle]) { return middle; } if (x > a[middle]) { left = middle + 1; } else { right = middle - 1; } } return -1; }