折半查找

#include <stdio.h>/*练习3-1改进折半查找*/int binsearch(int x, int v[], int n);int main(){int v[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};printf("%d\n", binsearch(9, v, 10));return 0;}/* binsearch: find x in v[0] <= v[1] <= ... <= v[n1]*/int binsearch(int x, int v[], int n){int low, high, mid;low = 0;high = n-1;while (low < high) {mid = (low+high)/2;if (x <= v[mid])high = mid;//上限只能在high之内elselow = mid + 1;//下限在low之后}return (x == v[low])?low:-1;}