代码随想录训练营 单调栈

代码随想录训练营 单调栈

• 739. 每日温度🌸
• 496. 下一个更大元素 I🌸

739. 每日温度🌸

func dailyTemperatures(temperatures []int) []int {
    res := make([]int, len(temperatures))
    // 初始化栈顶元素为第一个下标索引0
    stack := []int{0}

    for i := 1; i < len(temperatures); i++ {
        top := stack[len(stack)-1]
        if temperatures[i] < temperatures[top] {
            stack = append(stack, i)
        } else if temperatures[i] ==  temperatures[top] {
            stack = append(stack, i)
        } else {
            for len(stack) != 0 && temperatures[i] > temperatures[top] {
                res[top] = i - top
                stack = stack[:len(stack)-1]
                if len(stack) != 0 {
                    top = stack[len(stack)-1]
                }
            }
            stack = append(stack, i)
        }
    }
    return res
}

496. 下一个更大元素 I🌸

func nextGreaterElement(nums1 []int, nums2 []int) []int {
    res := make([]int, len(nums1))
    for i := range res { res[i] = -1 }
    m := make(map[int]int, len(nums1))
    for k, v := range nums1 { m[v] = k }

    stack := []int{0}
    for i := 1; i < len(nums2); i++ {
        top := stack[len(stack)-1]
        if nums2[i] < nums2[top] {
            stack = append(stack, i)
        } else if nums2[i] == nums2[top] {
            stack = append(stack, i)
        } else {
            for len(stack) != 0 && nums2[i] > nums2[top] {
                if v, ok := m[nums2[top]]; ok {
                    res[v] = nums2[i]
                }
                stack = stack[:len(stack)-1]
                if len(stack) != 0 {
                    top = stack[len(stack)-1]
                }
            }
            stack = append(stack, i)
        }
    }
    return res
}