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57 lines
1.1 KiB
Go
57 lines
1.1 KiB
Go
package leetcode
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import (
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"math"
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)
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// 解法一 倒序 DP，无辅助空间
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func minimumTotal(triangle [][]int) int {
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if triangle == nil {
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return 0
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}
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for row := len(triangle) - 2; row >= 0; row-- {
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for col := 0; col < len(triangle[row]); col++ {
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triangle[row][col] += min(triangle[row+1][col], triangle[row+1][col+1])
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}
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}
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return triangle[0][0]
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}
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func min(a int, b int) int {
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if a > b {
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return b
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}
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return a
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}
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// 解法二 正常 DP，空间复杂度 O(n)
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func minimumTotal1(triangle [][]int) int {
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if len(triangle) == 0 {
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return 0
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}
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dp, minNum, index := make([]int, len(triangle[len(triangle)-1])), math.MaxInt64, 0
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for ; index < len(triangle[0]); index++ {
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dp[index] = triangle[0][index]
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}
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for i := 1; i < len(triangle); i++ {
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for j := len(triangle[i]) - 1; j >= 0; j-- {
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if j == 0 {
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// 最左边
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dp[j] += triangle[i][0]
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} else if j == len(triangle[i])-1 {
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// 最右边
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dp[j] += dp[j-1] + triangle[i][j]
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} else {
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// 中间
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dp[j] = min(dp[j-1]+triangle[i][j], dp[j]+triangle[i][j])
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}
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}
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}
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for i := 0; i < len(dp); i++ {
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if dp[i] < minNum {
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minNum = dp[i]
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}
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}
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return minNum
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}
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