leetcode 97. 交錯字串 #dp #掌握!
阿新 • • 發佈:2020-12-26
97. 交錯字串
Difficulty: 困難
給定三個字串s1
、s2
、s3
,請你幫忙驗證s3
是否是由s1
和s2
交錯 組成的。
兩個字串 s
和 t
交錯 的定義與過程如下,其中每個字串都會被分割成若干 非空 子字串:
s = s<sub style="display: inline;">1</sub> + s<sub style="display: inline;">2</sub> + ... + s<sub style="display: inline;">n</sub>
t = t<sub style="display: inline;">1</sub> + t<sub style="display: inline;">2</sub> + ... + t<sub style="display: inline;">m</sub>
|n - m| <= 1
- 交錯 是
s<sub style="display: inline;">1</sub> + t<sub style="display: inline;">1</sub> + s<sub style="display: inline;">2</sub> + t<sub style="display: inline;">2</sub> + s<sub style="display: inline;">3</sub> + t<sub style="display: inline;">3</sub> + ...
t<sub style="display: inline;">1</sub> + s<sub style="display: inline;">1</sub> + t<sub style="display: inline;">2</sub> + s<sub style="display: inline;">2</sub> + t<sub style="display: inline;">3</sub> + s<sub style="display: inline;">3</sub> + ...
提示:a + b
意味著字串 a
和 b
連線。
示例 1:
輸入:s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"
輸出:true
示例 2:
輸入:s1 = "aabcc", s2 = "dbbca", s3 = "aadbbbaccc"
輸出:false
示例 3:
輸入:s1 = "", s2 = "", s3 = ""
輸出:true
提示:
0 <= s1.length, s2.length <= 100
0 <= s3.length <= 200
s1
、s2
、和s3
都由小寫英文字母組成
Solution
Language: ****
class Solution {
public:
bool isInterleave(string s1, string s2, string s3) {
int n = s1.size() ,m = s2.size();
if (n+m != s3.size()) return false;
vector< vector<bool>> dp(n+1, vector<bool>(m+1, false));
s1 = '#' + s1,s2 = '#' + s2,s3 = '#' + s3;
//當 i = 1
dp[0][0] = true;
for (int i=1;i<=n;++i) dp[i][0] = s1[i] == s3[i] && dp[i-1][0];
for (int j=1; j<=m;++j) dp[0][j] = s2[j] == s3[j] && dp[0][j-1];
//當 j = 1
for (int i=1; i<=n;++i) {
for (int j = 1; j<=m;++j) {
//s1 區了 i 個, s2 取出j 個
if(s1[i] == s3[j+i] && dp[i-1][j]) dp[i][j] = true;
else if(s2[j] == s3[i+j] && dp[i][j-1]) dp[i][j] = true;
}
}
return dp[n][m];
}
};
/*
dp[i][j]
考慮方向
dp[i-1][j]
dp[i][j-1]
dp[i-1][j-1];
思路:
aaaaaa(i)
bbbbbbb
ccccccccccccc(z)
*/