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Update 0704.二分查找.md
add detailed comments to the Javascript version of Binary Search
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@ -276,7 +276,7 @@ func search(nums []int, target int) int {
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```
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```
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**JavaScript:**
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**JavaScript:**
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(版本一)左闭右闭区间
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(版本一)左闭右闭区间 [left, right]
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```js
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```js
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/**
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/**
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@ -285,10 +285,12 @@ func search(nums []int, target int) int {
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* @return {number}
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* @return {number}
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*/
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*/
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var search = function(nums, target) {
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var search = function(nums, target) {
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// right是数组最后一个数的下标,num[right]在查找范围内,是左闭右闭区间
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let left = 0, right = nums.length - 1;
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let left = 0, right = nums.length - 1;
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// 使用左闭右闭区间
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// 当left=right时,由于nums[right]在查找范围内,所以要包括此情况
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while (left <= right) {
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while (left <= right) {
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let mid = left + Math.floor((right - left)/2);
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let mid = left + Math.floor((right - left)/2);
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// 如果中间数大于目标值,要把中间数排除查找范围,所以右边界更新为mid-1;如果右边界更新为mid,那中间数还在下次查找范围内
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if (nums[mid] > target) {
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if (nums[mid] > target) {
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right = mid - 1; // 去左面闭区间寻找
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right = mid - 1; // 去左面闭区间寻找
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} else if (nums[mid] < target) {
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} else if (nums[mid] < target) {
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@ -300,7 +302,7 @@ var search = function(nums, target) {
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return -1;
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return -1;
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};
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};
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```
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```
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(版本二)左闭右开区间
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(版本二)左闭右开区间 [left, right)
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```js
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```js
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/**
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/**
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@ -309,10 +311,13 @@ var search = function(nums, target) {
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* @return {number}
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* @return {number}
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*/
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*/
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var search = function(nums, target) {
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var search = function(nums, target) {
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// right是数组最后一个数的下标+1,nums[right]不在查找范围内,是左闭右开区间
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let left = 0, right = nums.length;
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let left = 0, right = nums.length;
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// 使用左闭右开区间 [left, right)
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// 当left=right时,由于nums[right]不在查找范围,所以不必包括此情况
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while (left < right) {
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while (left < right) {
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let mid = left + Math.floor((right - left)/2);
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let mid = left + Math.floor((right - left)/2);
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// 如果中间值大于目标值,中间值不应在下次查找的范围内,但中间值的前一个值应在;
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// 由于right本来就不在查找范围内,所以将右边界更新为中间值,如果更新右边界为mid-1则将中间值的前一个值也踢出了下次寻找范围
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if (nums[mid] > target) {
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if (nums[mid] > target) {
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right = mid; // 去左区间寻找
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right = mid; // 去左区间寻找
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} else if (nums[mid] < target) {
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} else if (nums[mid] < target) {
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