如何在数组中找到元素的位置（C 编程）

Question

I have a function that asks the user to input 10 integers into an array then finds the max value of the array.

int largestPos(int array[], int size, int index) {

int k, maxVal = 0;

printf("Enter a starting index: ");
scanf("%d", &index);

for (k = index; k < size; k++){
    if (maxVal < array[k]){
        maxVal = array[k];
    }
}
printf("The maximum value is %d at position %d \n", maxVal, array[maxVal]);

return 0;

}

The max value calculates correct. But when I try to find the position of the max value, I get a crazy number. What is wrong with the way I am finding the position of the max value?

Answer 1

int maxPos=0;    

for (k = index; k < size; k++){
        if (maxVal < array[k]){
            maxVal = array[k];
            maxPos = k;
        }
    }    

    printf("The maximum value is %d at position   %d \n", 
maxVal, maxPos);

Answer 2

The following will only find the max value if all the integers are greater than zero. If they're all negative integers then the max value here would be 0.

int array[5] = {-234, -133, -581, -8, -41};

int maxVal = 0;

for(i = 0; i < size; ++i) {
    if(array[i] > maxVal) {
        maxVal = array[i];
    }
}

Instead you want to initialize maxVal with the first element inside the array, then compare every other element to it (skipping the first element in the for loop so you're not comparing maxVal to itself). This will give the max value of -8 at index 3.

int array[5] = {-234, -133, -581, -8, -41};

// initialize maxVal to first element inside the array
int maxVal = array[0];
int pos = 0;

for(i = 1; i < size; ++i) {
    if(array[i] > maxVal) {
        maxVal = array[i];
        // Find the index of the max value
        pos = i;
    }
}

Answer 3

Imagine you have this array : {100 , 99 , 98 , 97 , 96 , 95 , 94 , 93 , 92 , 91 , 90}, the max value is 100. Your code tries to print array[maxValue] so array[100].

Maybe you should not save the value into maxValue but rather the position to get something correct