leetcode

Daily Problem

2 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/ Problems/1269.cpp b/ Problems/1269.cpp

@@ -0,0 +1,43 @@

// Top-down DP

class Solution {

static const int MOD = 1E9 + 7;

int dp[501][501];

public:

Solution() { memset(dp, 0xFF, sizeof(dp)); }

int numWays(const int steps, const int arrLen, const int crnt = 0) {

if (steps == 0) return crnt == 0;

if (dp[crnt][steps] != -1) return dp[crnt][steps];

int res = numWays(steps - 1, arrLen, crnt);

if (crnt > 0) res = (res + numWays(steps - 1, arrLen, crnt - 1)) % MOD;

if (crnt < arrLen - 1) res = (res + numWays(steps - 1, arrLen, crnt + 1)) % MOD;

return dp[crnt][steps] = res;

}

};

// Space optimized, bottom-up DP

class Solution {

static const int MOD = 1E9 + 7;

static int dp[501], pdp[501];

public:

int numWays(const int steps, int arrLen) {

memset(pdp, 0x00, sizeof(pdp));

arrLen = min(arrLen, steps), pdp[0] = 1;

for (int remain = 1; remain <= steps; remain++) {

for (int crnt = arrLen - 1; crnt >= 0; crnt--) {

int res = pdp[crnt];

if (crnt > 0) res = (res + pdp[crnt - 1]) % MOD;

if (crnt < arrLen - 1) res = (res + pdp[crnt + 1]) % MOD;

dp[crnt] = res;

}

swap(dp, pdp);

}

return pdp[0];

}

};

int Solution::dp[501];

int Solution::pdp[501];

diff --git a/ README.md b/ README.md

@@ -552,6 +552,7 @@ for solving problems. | 1254 | Medium | [Number of Closed Islands](Problems/1254.cpp) | | 1261 | Medium | [Find Elements in a Contaminated Binary Tree](Problems/1261.cpp) | | 1268 | Medium | [Search Suggestions System](Problems/1268.cpp) |

| 1269 | Hard | [Number of Ways to Stay in the Same Place After Some Steps](Problems/1269.cpp) |

| 1277 | Medium | [Count Square Submatrices with All Ones](Problems/1277.cpp) | | 1282 | Medium | [Group the People Given the Group Size They Belong To](Problems/1282.cpp) | | 1286 | Medium | [Iterator for Combination](Problems/1286.cpp) |