leetcode35 Search Insert Position

題目要求：在一個有序的數組中，找到一個目標值，返回該值得下標。若沒有找到該值，則返回該值順序插入的下標
例如，
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

public int searchInsert(int[] nums, int target) {
        int index=0;
        for( ; index<nums.length ; index++){
            if(nums[index]>=target){
                break;
            }
        }
        return index;
    }

使用雙指針後效率比單指針效率高

public int searchInsert2(int[] nums, int target) {
        int pointerLeft = 0;
        int pointerRight = nums.length-1;
        for( ; pointerLeft<=pointerRight ; pointerLeft++, pointerRight--){
            if(nums[pointerLeft]>=target){
                return pointerLeft;
            }
            if(nums[pointerRight]<target){
                return pointerRight+1;
            }
        }
        return pointerLeft;
    }

使用二分法也能夠，可是二分法可能會在數組有重複數字狀況下產生多個答案

public int searchInsert3(int[] nums, int target) {
        int pointerLeft = 0;
        int pointerRight = nums.length-1;
        while(pointerLeft<=pointerRight){
            int mid = (pointerLeft+pointerRight)/2;
            if(nums[mid]==target){
                return mid;
            }else if(nums[mid]>target){
                pointerRight = mid-1;
            }else{
                pointerLeft = mid+1;
            }
        }
        return pointerLeft;
    }

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