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programmers/연습문제/보행자 천국/README.md

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+```java
+class Solution {
+ int MOD = 20170805;
+ public int solution(int m, int n, int[][] cityMap) {
+ int memo[][] = new int[m][n];
+ for(int i=0; i<m; i++){
+ for(int j=0; j<n; j++){
+ memo[i][j] = -1;
+ }
+ }
+ int a = helper(cityMap, memo, m-2, n-1, true);
+ int b = helper(cityMap, memo, m-1, n-2, false); 
+ return (a + b) % MOD;
+ }
+ public int helper(int[][] cityMap, int[][] memo, int m, int n, boolean flow){
+ if(m<0 || n<0 || cityMap[m][n]==1 ) return 0;
+ if(m==0 && n==0) return 1;
+ if(cityMap[m][n]==2){
+ if(flow) return helper(cityMap, memo, m-1, n, true);
+ else return helper(cityMap, memo, m, n-1, false);
+ }
+ if(memo[m][n]!=-1) return memo[m][n] % MOD;
+ memo[m][n] = helper(cityMap, memo, m-1, n, true) + 
+ helper(cityMap, memo, m, n-1, false);
+ return memo[m][n] % MOD;
+ }
+}
+```