g0401_0500.s0494_target_sum.solution.go Maven / Gradle / Ivy

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package s0494_target_sum

// #Medium #Top_100_Liked_Questions #Array #Dynamic_Programming #Backtracking
// #Big_O_Time_O(n*(sum+s))_Space_O(n*(sum+s)) #2024_03_12_Time_7_ms_(80.54%)_Space_6.6_MB_(40.47%)

import "math"

func findTargetSumWays(nums []int, s int) int {
	sum := 0
	s = int(math.Abs(float64(s)))
	for _, num := range nums {
		sum += num
	}

	if s > sum || (sum+s)%2 != 0 {
		return 0
	}

	dp := make([][]int, (sum+s)/2+1)
	for i := range dp {
		dp[i] = make([]int, len(nums)+1)
	}
	dp[0][0] = 1

	for i := 0; i < len(nums); i++ {
		if nums[i] == 0 {
			dp[0][i+1] = dp[0][i] * 2
		} else {
			dp[0][i+1] = dp[0][i]
		}
	}

	for i := 1; i < len(dp); i++ {
		for j := 0; j < len(nums); j++ {
			dp[i][j+1] += dp[i][j]
			if nums[j] <= i {
				dp[i][j+1] += dp[i-nums[j]][j]
			}
		}
	}

	return dp[(sum+s)/2][len(nums)]
}