Linux洗C语言基础编程——折半查找法

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今天我们写一个选择法排序与折半查找法相结合的程序。主要实现先排序在查找。前面我们已经详细的讲过了选择排序法，现在我们来说下折半查找法

折半查找法的主要思想是 number与mid的比较

mid = （butt+top）/2

如果number大于mid，则top = mid+1；

如果number小于mid，则butt = mid-1；

下面附上我的代码，如有不合理的地方，请指正！

#include <stdio.h>#define N 15void binsearch(int a[N])/*折半查找*/{int top;int but;int mid;int flag;int num;int sign;int loca;char c;flag = 1;while(flag){printf("input the number you want to search!");scanf("%d",&num);top = 0;sign = 0;but = N - 1;if((num < a[0]) && (num >a[N-1])){loca = -1;}while((!sign) && (top <= but)){mid = (top + but)/2;if(num == a[mid]){loca = mid;printf("Has found the number %d,its postion is %d\n",num,loca + 1);sign = 1;}else if(num > a[mid]){top = mid +1;}else{but = mid -1;}}if(!sign || loca == -1){printf("Can not find the number!\n");}printf("continue or no [Y/N]:\n");scanf(" %c",&c);if(c == 'N' || c == 'n'){flag = 0;}}}void choicearrange(int a[N])/*选择法排序*/{int i;int j;int k;int temp;for(i = 0; i < N-1; i++){k = i;for(j = i + 1; j < N; j++){if(a[k] > a[j]){k = j;}}if(k != i){temp = a[k];a[k] = a[i];a[i] = temp;}}}int main()/*主函数*/{int a[N];int i;for(i = 0; i < N; i++){scanf("%d",&a[i]);}choicearrange(a);for(i = 0 ;i < N; i++){printf("%-3d",a[i]);}printf("\n");binsearch(a);    return 0;}

程序运行结果见下图：

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