LeetCode 964: Least Operators to Express Number Solution
Master LeetCode problem 964 (Least Operators to Express Number), a hard challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
964. Least Operators to Express Number
Problem Explanation
Explanation
To solve this problem, we can use a recursive approach. The idea is to try all possible combinations of operations (+, -, *, /) between consecutive x values and keep track of the minimum number of operations needed to reach the target.
We can define a recursive function that takes the current sum, current value of x, the target value, and the number of operations used so far. At each step, we can recursively explore all possible operations and update the minimum number of operations needed to reach the target.
Time complexity: O(4^n) where n is the number of x values between the current sum and the target. Space complexity: O(n) for the recursive stack.
Solution Code
class Solution {
public int leastOpsExpressTarget(int x, int target) {
return solve(x, target, 0, 0) - 1;
}
private int solve(int x, int target, int pos, int cost) {
int val = (int) Math.pow(x, pos);
int diff = val * x - target;
if (diff == 0) {
return cost + 1;
} else if (diff < 0) {
return cost + 2 + solve(x, target - val, pos + 1, 0);
} else {
int right = solve(x, target - val, pos + 1, 0);
int left = solve(x, target + val, pos + 1, 0);
return Math.min(cost + pos + 1 + right, cost + pos + left);
}
}
}Try It Yourself
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