技術標籤：筆記

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

void print(int *source, int length) {
    for (int i = 0; i < length; i++) {
        printf("%d ", source[i]);
    }
    printf("\n");
}

/* 要生成和返回隨機數的函式 */
void getRandom(int *target, const int
 
 length) {
    /* 設定種子 */
    srand((unsigned) time(NULL));
    for (int i = 0; i < length; ++i) {
        target[i] = rand();
    }
}

void swap(int *x, int *y) {
    int t = *x;
    *x = *y;
    *y = t;
}

void copyArr(int *source, int *target, int start, int length) {
    // int length = sizeof(source) / sizeof(int);
 

    // 不在在這裡計算陣列的長度，這裡的source是指標的長度
    // 將陣列以引數的形式傳遞進來
    for (int i = start; i < length; i++) {
        target[i - start] = source[i];
    }
}

void sortArr(int *source, int n) {
    if (n < 2) { return; }
    if (n == 2) {
        if (source[0] > source[1]) {
            int tmp = source[0]
 
;
            source[0] = source[1];
            source[1] = tmp;
        }
    } else {
        // 1. 拆分成兩個陣列
        int leftHalfLength = n / 2;
        int rightHalfLength = n - leftHalfLength;
        int leftHalf[leftHalfLength];
        int rightHalf[rightHalfLength];
        copyArr(source, leftHalf, 0, leftHalfLength);
        copyArr(source, rightHalf, leftHalfLength, n);

        // 2. 遞迴呼叫sort
        sortArr(leftHalf, leftHalfLength);
        sortArr(rightHalf, rightHalfLength);

        // 3. 合併兩個有序陣列
        int leftIndex = 0, rightIndex = 0, index = 0;
        while (leftIndex < leftHalfLength || rightIndex < rightHalfLength) {
            if (leftIndex >= leftHalfLength) {
                while (rightIndex < rightHalfLength) {
                    source[index++] = rightHalf[rightIndex++];
                }
            }
            if (rightIndex >= rightHalfLength) {
                while (leftIndex < leftHalfLength) {
                    source[index++] = leftHalf[leftIndex++];
                }
            }
            source[index++] =
                    leftHalf[leftIndex] < rightHalf[rightIndex] ? leftHalf[leftIndex++] : rightHalf[rightIndex++];
        }

    }
}

int main() {
    int length = 15;
	printf("input a number:");
	scanf("%d",&length);
	if(length<1){
		return 1;
	}
    int arr[length];
    getRandom(arr, length);
    print(arr, length);
    sortArr(arr, length);
    print(arr, length);
	char a[20];
	scanf("%s",&a);
    return 0;
}