Problem 396: Rotate Function
思路
通过观察可以发现:
F(0) = 0A + 1B + 2C +3D
F(1) = 0D + 1A + 2B +3C
F(2) = 0C + 1D + 2A +3B
F(3) = 0B + 1C + 2D +3A
等同于:
F(1) = F(0) + sum - 4D
F(2) = F(1) + sum - 4C
F(3) = F(2) + sum - 4B
从而得出递推关系:
public class Solution {
public int maxRotateFunction(int[] A) {
int len = A.length;
int sum = 0;
int f = 0;
for (int i = 0; i < len; i++) {
f += i * A[i];
sum += A[i];
}
int max = f;
for (int i = 1; i < len; i++) {
f = f + sum - len * A[len - i];
max = Math.max(max, f);
}
return max;
}
}
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