Int To Hex

Day20200714.cpp

@@ -19,6 +19,9 @@ int firstUniqChar(char *s);
  * */
 char *toHex(int num);
 
+// 滑动窗口
+char *toHex2(int num);
+
 /**
  * 给定一个数组 nums，编写一个函数将所有 0 移动到数组的末尾，同时保持非零元素的相对顺序。
  * */
@@ -40,20 +43,49 @@ int firstUniqChar(char *s) {
 
 char *toHex(int num) {
 
-    char hash[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+    char table[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+    char *res = (char *) calloc(9, sizeof(char));
+    // 最长 8 位！
+    int idx = 7, cnt = 8;
+    // 倒置填充索引与计数器
+    do {
+        int lowbit4 = num & 0xf;
+        res[idx--] = table[lowbit4];
+        num >>= 4;
+        cnt -= 1;
+        printf("res = %s\n",res);
+        printf("low = %c\n",table[lowbit4]);
+    } while (num != 0 && cnt > 0);
+    // TODO  wtf ???
+    return res + idx + 1;  // 地址截取
+}
 
+char *toHex2(int num) {
 
-    return hash;
-}
+    char table[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+    // 最长 8 位 ！
+    char *res = (char *) calloc(9, sizeof(char));
+    res[0] = '0';
+    int move = 28;
+    int index = 0;
+    unsigned int highbit4 = 0xf0000000;
 
-void moveZeroes(int *nums, int numsSize) {
+    while (highbit4 != 0) {
+        int result = (num & highbit4) >> move;
+        if (result != 0 || res[0] != '0') {
+            res[index++] = table[result];
+        }
+        move -= 4;
+        highbit4 >>= 4;
+    }
 
+    return res;  // 地址截取
+}
 
+void moveZeroes(int *nums, int numsSize) {
     for (int i = 0; i < numsSize; ++i) {
         printf("%d ", nums[i]);
     }
-
-
 }
 
 
@@ -62,11 +94,12 @@ void test();
 void test() {
 
     char *s = "abcabacdef";
-    printf("firstUniqChar:%d\n", firstUniqChar(s));
-//    printf("toHex(%d) = %s\n", 5, toHex(5));
+//    printf("firstUniqChar:%d\n", firstUniqChar(s));
+
+    printf("toHex(%p) = %s\n", 255, toHex(255));
 
-    int nums[] = {0, 1, 2, 5, 0, 6, 0, 7};
-    moveZeroes(nums, 8);
+//    int nums[] = {0, 1, 2, 5, 0, 6, 0, 7};
+//    moveZeroes(nums, 8);
 
 
 }
@@ -76,6 +109,5 @@ int main() {
 
     test();
 
-
 }