Binary search line of code

Question

I've been trying to learn how the binary search works, so I searched for a code and tried to understand what each line does. There is this one line that I don't understand. The line with the "return -1". I don't understand what that means. Can someone explain what happens in that line of code?

 #include<stdio.h>

int binarySearch(int array[], int size, int searchValue){
int low = 0;
int high = size - 1;

while(low<=high){// is the array exhausted?
    int mid = (low + high) / 2; //If not, find the middle index

    if(searchValue == array[mid]){
        return mid;
    }
    else if(searchValue > array[mid]){
        low = mid + 1;
    }
    else{
        high = mid - 1;
    }
}
return -1;
}

int main(){
int array[] = {1,2,3,4,5,6,7};
int searchNum;

printf("Enter an integer:");
scanf("%d", &searchNum);

int result = binarySearch(array,7,searchNum);

if(result>=0){
    printf("Found!");
}
else{
    printf("Not found!");
}
getch();
}

Answer 1

在数组中执行二进制搜索，并且数组的位置从0开始。因此，如果返回-1，则意味着该位置不在数组中或无法找到。

Answer 2

The while loop is performed and contains a return statement, if the item you are looking for is in the array, then the return in the while loop will return the index of the item. The return -1 statement that follows returns to the caller if the item is not found, ie if high>low , -1 is used to indicate that it is in the array as an index of -1 is outside the bounds of any array. Without the return -1 statement then there would be a compile time error saying that the return statement is missing

When you perform your check

if(result>=0) {
printf("Found!");
} else {
printf("Not found!");
}

If the binary search method finds the item and returns the index(which will be >-1) then "Found! will be printed to the console, else if the binary search method returns a value <0, ie -1 then the item has not been found in the array, and thus Not Found! is printed to the console, your if statement alone can give your binary search a good explantation!