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solution.ts
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solution.ts
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// #Medium #Top_100_Liked_Questions #Array #Dynamic_Programming #Backtracking
// #Big_O_Time_O(n*(sum+s))_Space_O(n*(sum+s))
// #2023_09_30_Time_77_ms_(81.99%)_Space_48.3_MB_(62.73%)
function findTargetSumWays(nums: number[], s: number): number {
let sum: number = 0
s = Math.abs(s)
for (const num of nums) {
sum += num
}
// Invalid s, just return 0
if (s > sum || (sum + s) % 2 !== 0) {
return 0
}
const dp: number[][] = new Array((sum + s) / 2 + 1).fill(null).map(() => new Array(nums.length + 1).fill(0))
dp[0][0] = 1
// Empty knapsack must be processed specially
for (let i = 0; i < nums.length; i++) {
if (nums[i] === 0) {
dp[0][i + 1] = dp[0][i] * 2
} else {
dp[0][i + 1] = dp[0][i]
}
}
for (let i = 1; i < dp.length; i++) {
for (let j = 0; j < nums.length; 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][nums.length]
}
export { findTargetSumWays }