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a_413.java
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33 lines (31 loc) · 924 Bytes
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package dynamicProgramming;
/**
* 等差数列划分
*/
public class a_413 {
/*
dp[i] 表示以 A[i] 为结尾的等差递增子区间的个数。
在 A[i] - A[i - 1] == A[i - 1] - A[i - 2] 的条件下，
{A[i - 2], A[i - 1], A[i]} 是一个等差递增子区间。如
果 {A[i - 3], A[i - 2], A[i - 1]} 是一个等差递增子区
间，那么 {A[i - 3], A[i - 2], A[i - 1], A[i]} 也是等
差递增子区间，dp[i] = dp[i-1] + 1。
*/
public int numberOfArithmeticSlices(int[] A) {
if (A.length == 0 && A == null) {
return 0;
}
int n = A.length;
int[] dp = new int[n];
for (int i = 2; i < n; i++) {
if (A[i-1]-A[i-2] == A[i]-A[i-1]) {
dp[i] = dp[i-1] + 1;
}
}
int totle = 0;
for (int cnt : dp) {
totle += cnt;
}
return totle;
}
}