Target Sum 25 XP Medium

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Assign + or - to each number in an array to make the sum equal to target. Count the number of ways.

nums = [1, 1, 1, 1, 1], target = 3
# -1+1+1+1+1 = 3
# +1-1+1+1+1 = 3
# +1+1-1+1+1 = 3
# +1+1+1-1+1 = 3
# +1+1+1+1-1 = 3
# Answer: 5 ways

Use a hashmap DP: dp[sum] = number of ways to reach that sum. Process each number, updating possible sums.

💡 Pro tip: Understand this problem deeply — don't just memorize the code. Try explaining the approach out loud as if teaching a friend. If you can explain it simply, you truly understand it!

📋 Instructions

Count ways to assign +/- to reach target. nums=[1,1,1,1,1], target=3.

Use Counter/dict. Start with {0: 1}. For each num, create new dict: for each (s, count), add to s+num and s-num.

🧪 Test Cases

Input

findTargetSumWays([1,1,1,1,1], 3)

Expected

5

Test case 1

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main.py

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Output

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