排序

一、快排

int getRandom(int start, int end) {
    srand((int)time(0));
    int idx = random() % (end - start + 1) + start;
    return idx;
}

int partition(int *a, int len, int start, int end) {
    int idx = getRandom(start, end);
    if (idx != end) {
        swap(a[idx], a[end]);
    }
    
    int small = start - 1;
    for (idx = start; idx < end; ++ idx) {
        if (a[idx] < a[end]) {
            ++ small;
            if (small != idx) {
                swap(a[idx], a[small]);
            }
        }
    }
    
    ++ small;
    swap(a[small], a[end]);
    
    return small;
}

void quitSort(int *a, int len, int start, int end) {
    if (start == end) {
        return;
    }
    int idx = partition(a, len, start, end);
    if (idx > start) {
        quitSort(a, len, start, idx - 1);
    }
    if (idx < end) {
        quitSort(a, len, idx + 1, end);
    }
}

void myQuitSort(int *a, int len) {
    quitSort(a, len, 0, len - 1);
}