leetcode刷题记录-go版本（1、20、53、70、121、136）

为了秋招，从今天开始每天至少在leetcode上刷五道题。同时为了加强go的学习，我准备后面做题先用go语言来做。由于今天是第一题，先做简单题就不写做题思路，直接写代码了。

//leetcode136
func singleNumber(nums []int) int {
	ans := nums[0]
	for i := 1; i < len(nums); i++{
		ans ^= nums[i]
	}
	return ans
}


//leetcode121
func maxProfit(prices []int) int {
	ans := 0
	minVal := prices[0]
	for i := 1; i < len(prices); i++{
		ans = max(ans, prices[i] - minVal)
		minVal = min(minVal, prices[i])
	}
	return ans
}
func min(a, b int)int{
	if a < b{
		return a
	}else{
		return b
	}
}

func max(a, b int)int{
	if a > b{
		return a
	}else{
		return b
	}
}
func climbStairs(n int) int {
	if n == 1{
		return 1
	}else{
		a, b := 1, 1
		for i := 2; i <= n; i++{
			a , b = b, a + b
		}
		return b
	}
}

//leetcode53
func maxSubArray(nums []int) int {
	ans := nums[0]
	for i := 1; i < len(nums); i++{

		nums[i] = max(nums[i], nums[i] + nums[i - 1])
		ans = max(ans, nums[i])
	}
	return ans
}

//leetcode20
func isMatch(stack []byte, ch byte)bool{
	i := len(stack) - 1
	if((stack[i] == '{' && ch == '}' ) || (stack[i] == '[' && ch == ']') || (stack[i] == '(' && ch == ')')){
		return true
	}else{
		return false
	}
}

func isValid(s string) bool {
	var stack []byte
	for i := 0; i < len(s); i++{
		if(len(stack) == 0 || !isMatch(stack, s[i])){
			stack = append(stack, s[i])
		}else{
			stack = stack[:len(stack) - 1]
		}
	}
	return len(stack) == 0
}

func quickSort(nums []int, begin int, end int){
	if begin < end{
		left, right := begin, end
		key := nums[left]
		for left < right{
			for left < right && nums[right] >= key{
				right--
			}
			nums[left] = nums[right]
			for left < right && nums[left] <= key{
				left++
			}
			nums[right] = nums[left]
		}
		nums[left] = key
		quickSort(nums, begin, left - 1)
		quickSort(nums, left + 1, end)
	}
}

//leetcode1
func twoSum(nums []int, target int) []int {
    //quickSort(nums, 0, len(nums))
    ump := make(map[int]int)
    for i := 0; i < len(nums); i++{
        _, ok := ump[target - nums[i]]
        if ok{
            return []int{i, ump[target - nums[i]]}
        }else{
            ump[nums[i]] = i;
        }
        
    }
    return []int{-1,-1}
}