用一段C语言实现简单选择排序、直接插入排序和冒泡排序。

好的，以下是三种排序算法的C语言实现：

1. 简单选择排序：

void selection_sort(int arr[], int n) {
    int i, j, min_idx;
    for (i = 0; i < n-1; i++) {
        min_idx = i;
        for (j = i+1; j < n; j++) {
            if (arr[j] < arr[min_idx]) {
                min_idx = j;
            }
        }
        // Swap the found minimum element with the first element
        int temp = arr[min_idx];
        arr[min_idx] = arr[i];
        arr[i] = temp;
    }
}

2. 直接插入排序：

void insertion_sort(int arr[], int n) {
    int i, j, key;
    for (i = 1; i < n; i++) {
        key = arr[i];
        j = i - 1;
        // Move elements of arr[0..i-1], that are greater than key, to one position ahead of their current position
        while (j >= 0 && arr[j] > key) {
            arr[j+1] = arr[j];
            j = j - 1;
        }
        arr[j+1] = key;
    }
}

3. 冒泡排序：

void bubble_sort(int arr[], int n) {
    int i, j;
    for (i = 0; i < n-1; i++) {
        // Last i elements are already in place
        for (j = 0; j < n-i-1; j++) {
            if (arr[j] > arr[j+1]) {
                // Swap arr[j] and arr[j+1]
                int temp = arr[j];
                arr[j] = arr[j+1];
                arr[j+1] = temp;
            }
        }
    }
}

这些算法都是经典的排序算法，可以用于对数组进行排序。