741. Cherry Pickup

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class Solution {
public int cherryPickup(int[][] grid) {
int n = grid.length;

int[][][] dp = new int[2 * n - 1][n][n];
for (int i = 0; i < dp.length; i++) {
for (int j = 0; j < n; j++) {
for (int k = 0; k < n; k++) {
dp[i][j][k] = Integer.MIN_VALUE;
}
}
}

dp[0][0][0] = grid[0][0];

for (int k = 1; k < dp.length; k++) {
for (int i1 = 0; i1 <= Math.min(k, n - 1); i1++) {
int j1 = k - i1;
for (int i2 = 0; i2 <= Math.min(k, n - 1); i2++) {
int j2 = k - i2;
if (j1 < 0 || j1 > n - 1 || j2 < 0 || j2 > n - 1) {
continue;
}

int v1 = grid[i1][j1], v2 = grid[i2][j2];
if (v1 == -1 || v2 == -1) {
continue;
}

int res = dp[k - 1][i1][i2];
if (i1 > 0) {
res = Math.max(res, dp[k - 1][i1 - 1][i2]);
}
if (i2 > 0) {
res = Math.max(res, dp[k - 1][i1][i2 - 1]);
}
if (i1 > 0 && i2 > 0) {
res = Math.max(res, dp[k - 1][i1 - 1][i2 - 1]);
}

res += v1;
if (i1 != i2) {
res += v2;
}

dp[k][i1][i2] = res;
}
}
}

return Math.max(0, dp[2 * n - 2][n - 1][n - 1]);
}
}

References

741. Cherry Pickup