g0401_0500.s0494_target_sum.Solution.kt Maven / Gradle / Ivy
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Kotlin-based LeetCode algorithm problem solutions, regularly updated
package g0401_0500.s0494_target_sum
// #Medium #Top_100_Liked_Questions #Array #Dynamic_Programming #Backtracking
// #2022_09_16_Time_308_ms_(89.61%)_Space_37.2_MB_(61.04%)
@Suppress("NAME_SHADOWING")
class Solution {
fun findTargetSumWays(nums: IntArray, s: Int): Int {
var s = s
var sum = 0
s = Math.abs(s)
for (num in nums) {
sum += num
}
// Invalid s, just return 0
if (s > sum || (sum + s) % 2 != 0) {
return 0
}
val dp = Array((sum + s) / 2 + 1) { IntArray(nums.size + 1) }
dp[0][0] = 1
// empty knapsack must be processed specially
for (i in nums.indices) {
if (nums[i] == 0) {
dp[0][i + 1] = dp[0][i] * 2
} else {
dp[0][i + 1] = dp[0][i]
}
}
for (i in 1 until dp.size) {
for (j in nums.indices) {
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][nums.size]
}
}