You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
59 lines
1.9 KiB
59 lines
1.9 KiB
/**
|
|
* File: binary_search_edge.c
|
|
* Created Time: 2023-05-31
|
|
* Author: Gonglja (glj0@outlook.com)
|
|
*/
|
|
|
|
#include "../utils/common.h"
|
|
|
|
|
|
/* 二分查找最左一个元素 */
|
|
int binarySearchLeftEdge(int *nums, int size, int target) {
|
|
int i = 0, j = size - 1; // 初始化双闭区间 [0, n-1]
|
|
while (i <= j) {
|
|
int m = i + (j - i) / 2; // 计算中点索引 m
|
|
if (nums[m] < target)
|
|
i = m + 1; // target 在区间 [m+1, j] 中
|
|
else if (nums[m] > target)
|
|
j = m - 1; // target 在区间 [i, m-1] 中
|
|
else
|
|
j = m - 1; // 首个小于 target 的元素在区间 [i, m-1] 中
|
|
}
|
|
if (i == size || nums[i] != target)
|
|
return -1; // 未找到目标元素，返回 -1
|
|
return i;
|
|
}
|
|
|
|
/* 二分查找最右一个元素 */
|
|
int binarySearchRightEdge(int *nums, int size, int target) {
|
|
int i = 0, j = size - 1; // 初始化双闭区间 [0, n-1]
|
|
while (i <= j) {
|
|
int m = i + (j - i) / 2; // 计算中点索引 m
|
|
if (nums[m] < target)
|
|
i = m + 1; // target 在区间 [m+1, j] 中
|
|
else if (nums[m] > target)
|
|
j = m - 1; // target 在区间 [i, m-1] 中
|
|
else
|
|
i = m + 1; // 首个大于 target 的元素在区间 [m+1, j] 中
|
|
}
|
|
if (j < 0 || nums[j] != target)
|
|
return -1; // 未找到目标元素，返回 -1
|
|
return j;
|
|
}
|
|
|
|
/* Driver Code */
|
|
int main() {
|
|
int target = 6;
|
|
int nums[] = {1, 3, 6, 6, 6, 6, 6, 10, 12, 15};
|
|
int size = sizeof(nums) / sizeof(nums[0]);
|
|
|
|
// 二分查找最左一个元素
|
|
int indexLeft = binarySearchLeftEdge(nums, size, target);
|
|
printf("数组中最左一个元素 6 的索引 = %d\n", indexLeft);
|
|
|
|
// 二分查找最右一个元素
|
|
int indexRight = binarySearchRightEdge(nums, size, target);
|
|
printf("数组中最右一个元素 6 的索引 = %d\n", indexRight);
|
|
|
|
return 0;
|
|
} |