算法之二分查找(c语言版实现+测试)

递归算法(deep是为了测试,实际生产不需要):
核心算法:

//递归算法int rank(Type key,Type a[],int lo,int hi,int deep){    if(lo > hi) return -1;    int mid = lo + (hi - lo) / 2;    printf("deep: %d lo: %d hi: %d\n",deep,lo,hi);    if (key > a[mid])    {        ++deep;        return rank(key,a,mid + 1,hi,deep);    }    else if (key < a[mid])    {        ++deep;        return rank(key,a,lo,mid - 1,deep);    }    else        return mid;}int BinarySearch(Type key,Type a[],int length){    int deep = 0;    return rank(key,a,0,length,deep);}

辅助排序函数（快速排序):

void QuickSort(Type a[],int left,int right){    Type temp;    if(left < right)    {        int i = left;        int j = right;        temp = a[left];        do       {          while(i < j && a[j] > temp)            --j;          if(i < j)            a[i++] = a[j];          while(i < j && a[i] < temp)              ++i;          if(i < j)              a[j--] = a[i];        }while(i != j);        a[i] = temp;        QuickSort(a,left,i-1);        QuickSort(a,i + 1,right);    }}

测试代码:

void test(char *mode,char *file){    //得到test 数组    FILE *fp;    if ((fp = fopen(file,"r")) == NULL)    {        return;    }    int count = 0;    int temp;    while (fscanf(fp,"%d",&temp) != EOF)        ++count;    fseek(fp,0,SEEK_SET);    Type a[count];    int pos = 0;    while(fscanf(fp,"%d",&a[pos++]) != EOF);    QuickSort(a,0,count - 1);    Type key;    if(strcmp(mode,"exist") == 0)    {        while(scanf("%d",&key) != EOF)        {            if(BinarySearch(key,a,sizeof(a)/sizeof(Type)-1) != -1)            {                printf("the key %d is exist in %s\n",key,file);            }        }    }    if(strcmp(mode,"noexist") == 0)    {        while(scanf("%d",&key) != EOF)        {            if(BinarySearch(key,a,sizeof(a)/sizeof(Type)-1) != -1)            {                printf("the key %d is not exist in %s\n",key,file);            }        }    }}

main.c

int main(){    test("exist","test.txt");    return 0;}

非递归算法:

//非递归算法int BinarySearch(Type key,Type a[],int hi){    int lo = 0;    while(lo <= hi)    {        int mid = lo + (hi - lo) / 2;        if (a[mid] > key)            hi = mid - 1;        else if (a[mid] < key)            lo = mid + 1;        else            return mid;    }    return -1;}

辅助排序函数(快速排序):

void QuickSort(Type a[],int left,int right){    Type temp;    if(left < right)    {        int i = left;        int j = right;        temp = a[left];        do       {          while(i < j && a[j] > temp)            --j;          if(i < j)            a[i++] = a[j];          while(i < j && a[i] < temp)              ++i;          if(i < j)              a[j--] = a[i];        }while(i != j);        a[i] = temp;        QuickSort(a,left,i-1);        QuickSort(a,i + 1,right);    }}

测试代码:

void test(char *mode,char *file){    //得到test 数组    FILE *fp;    if ((fp = fopen(file,"r")) == NULL)    {        return;    }    int count = 0;    int temp;    while (fscanf(fp,"%d",&temp) != EOF)        ++count;    fseek(fp,0,SEEK_SET);    Type a[count];    int pos = 0;    while(fscanf(fp,"%d",&a[pos++]) != EOF);    QuickSort(a,0,count - 1);    Type key;    if(strcmp(mode,"exist") == 0)    {        while(scanf("%d",&key) != EOF)        {            if(BinarySearch(key,a,sizeof(a)/sizeof(Type)-1) != -1)            {                printf("the key %d is exist in %s\n",key,file);            }        }    }    if(strcmp(mode,"noexist") == 0)    {        while(scanf("%d",&key) != EOF)        {            if(BinarySearch(key,a,sizeof(a)/sizeof(Type)-1) != -1)            {                printf("the key %d is not exist in %s\n",key,file);            }        }    }}

main.c

int main(){    test("exist","test.txt");    return 0;}