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Solution.cpp
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Solution.cpp
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// #Medium #Array #Dynamic_Programming #Backtracking #Big_O_Time_O(n*(sum+s))_Space_O(n*(sum+s))
// #2024_05_22_Time_8_ms_(70.29%)_Space_15.8_MB_(37.03%)
#include <vector>
#include <cmath>
using namespace std;
class Solution {
public:
int findTargetSumWays(vector<int>& nums, int s) {
int sum = 0;
s = abs(s);
for (int num : nums) {
sum += num;
}
// Invalid s, just return 0
if (s > sum || (sum + s) % 2 != 0) {
return 0;
}
int target = (sum + s) / 2;
vector<vector<int>> dp(target + 1, vector<int>(nums.size() + 1, 0));
dp[0][0] = 1;
// empty knapsack must be processed specially
for (int i = 0; i < nums.size(); i++) {
if (nums[i] == 0) {
dp[0][i + 1] = dp[0][i] * 2;
} else {
dp[0][i + 1] = dp[0][i];
}
}
for (int i = 1; i <= target; i++) {
for (int j = 0; j < nums.size(); j++) {
dp[i][j + 1] += dp[i][j];
if (nums[j] <= i) {
dp[i][j + 1] += dp[i - nums[j]][j];
}
}
}
return dp[target][nums.size()];
}
};