二分查找法

分别用循环和递归实现二分查找

#include <iostream>
using namespace std;
int binarysearchiteratively(int *data, int start, int end, int k){
    int l = start - 1;
    int r = end + 1;
    while (l + 1 != r){
        int middle = (l + r) / 2;
        if (data[middle] == k) return middle;
        else{
            if (data[middle] < k) l = middle;
            else{
                r = middle;
            }
        }
    }
    return -1;
}
int binarysearchrecursively(int *data, int start, int end, int k){
    if (start>end) return -1;
    int middle = (start + end) / 2;
    if (data[middle] == k){
        return middle;
    }
    else{
        if (data[middle] < k){
            return binarysearchrecursively(data,middle+1,end,k);
        }
        else{
            return  binarysearchrecursively(data, start, middle - 1, k);
        }
    }

}
void test1(){
    int a[] = { 1, 2, 3 };
    int result1 = binarysearchiteratively(a, 0, 2, 1);
    int result2 = binarysearchrecursively(a, 0, 2, 1);
    if (result1 == 0 && result2 == 0){
        printf("%s
", "test1 succeeded");
    }
    else{
        printf("%s
", "test1 failed");
    }
}
void test2(){
    int a[] = { 1, 2, 3 };
    int result1 = binarysearchiteratively(a, 0, 2, 4);
    int result2 = binarysearchrecursively(a, 0, 2, 4);
    if (result1 == -1 && result2 == -1){
        printf("%s
", "test2 succeeded");
    }
    else{
        printf("%s
", "test2 failed");
    }
}
void test3(){
    int a[] = { 1 };
    int result1 = binarysearchiteratively(a, 0, 0, 1);
    int result2 = binarysearchrecursively(a, 0, 0, 1);
    if (result1 == 0 && result2 == 0){
        printf("%s
", "test3 succeeded");
    }
    else{
        printf("%s
", "test3 failed");
    }
}
void test4(){
    int a[] = { 1 };
    int result1 = binarysearchiteratively(a, 0, 0, 2);
    int result2 = binarysearchrecursively(a, 0, 0, 2);
    if (result1 == -1 && result2 == -1){
        printf("%s
", "test4 succeeded");
    }
    else{
        printf("%s
", "test4 failed");
    }
}
int main(){
    test1();
    test2();
    test3();
    test4();
    system("pause");
}