122. Best Time to Buy and Sell Stock II


DP
time: O(n)
space:O(n)
class Solution {
public int maxProfit(int[] prices) {
int n = prices.length;
int dp[][] = new int[n][2];
dp[0][0] = 0;
dp[0][1] = -prices[0];
for (int i = 1; i < n ; i++) {
dp[i][0] = Math.max(dp[i-1][0], dp[i-1][1] + prices[i]);
dp[i][1] = Math.max(dp[i-1][1], dp[i-1][0] - prices[i]);
}
return dp[n-1][0];
}
}
use variable
ๆณจๆๅฐไธ้ข็็ๆ ่ฝ็งปๆน็จไธญ๏ผๆฏไธๅคฉ็็ๆ ๅช่ๅไธๅคฉ็็ๆ ๆ้๏ผ่่ๆดๆฉ็็ๆ ้ฝ็ก้๏ผๅ ๆญคๆๅไธๅฟ ๅญๅฒ้ไบ็ก้็็ๆ ๏ผ
ๅช้่ฆๅฐ dp[i-1] [0] , dp[i-1] [1] ๅญๆพๅจๅ ฉๅ่ฎ้ไธญ๏ผ้้ๅฎๅ่จ็ฎๅบ
dp[i] [0], dp [ i ] [ 1 ] ไธฆๅญๅๅฐๆ็่ฎ้
class Solution {
public int maxProfit(int[] prices) {
int n = prices.length;
int dp0 = 0;
int dp1 = -prices[0];
for (int i = 1; i < n ; i++) {
int newDp0 = Math.max(dp0, dp1 + prices[i]);
int newDp1 = Math.max(dp1, dp0 - prices[i]);
dp0 = newDp0;
dp1 = newDp1;
}
return dp0;
}
}
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