Solved 29

Author: mateusz-z-olszewski

src/leetcode/editor/en/[0029] Divide Two Integers.java

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+package leetcode.editor.en;
+
+class DivideTwoIntegers {
+
+//leetcode submit region begin(Prohibit modification and deletion)
+class Solution {
+    public int divide(int dividend, int divisor) {
+        int out = 0;
+        boolean isNegative = dividend < 0 ^ divisor < 0;
+        int remainingAbsDividend, absDivisor = abs(divisor);
+        // special cases for INT_MIN:
+        if(dividend == Integer.MIN_VALUE && divisor == Integer.MIN_VALUE) return 1;
+        if(divisor == Integer.MIN_VALUE) return 0; // nothing has absolute value greater than INT_MIN, so its 0
+        if(dividend == Integer.MIN_VALUE){
+            // only possibility for a result outside of integer range.
+            if(divisor == -1) return Integer.MAX_VALUE;
+            int shift = 1 + largestLesserEqLeftShift(1 << 30, absDivisor);
+            out = 1 << shift;
+            int subtract = absDivisor << shift;
+            remainingAbsDividend = dividend - subtract; // always positive
+        } else {
+            remainingAbsDividend = abs(dividend);
+        }
+        // normal cases
+        if(remainingAbsDividend < absDivisor) return isNegative ? neg(out) : out;
+        while(remainingAbsDividend >= absDivisor){
+            int lShift = largestLesserEqLeftShift(remainingAbsDividend, absDivisor);
+            remainingAbsDividend -= absDivisor << lShift;
+            out |= 1 << lShift;
+        }
+        return isNegative? neg(out) : out;
+    }
+
+    /**
+     * Returns by how many bits can toShift be shifted left to still be lesser or equal to limit.
+     * E.g. for limit=10010, toShift=101, result is 1 because 101<<1=1010, which is smaller than 10010.
+     * @param limit positive integer
+     * @param toShift positive integer
+     * @return
+     */
+    int largestLesserEqLeftShift(int limit, int toShift){
+        int i = 0;
+        while(limit >= toShift && toShift > 0) {
+            toShift <<= 1;
+            i++;
+        }
+        return i - 1;
+    }
+    int abs(int x){
+        return x >= 0 ? x : neg(x);
+    }
+    int neg(int x) {
+        return ~x + 1;
+    }
+
+}
+//leetcode submit region end(Prohibit modification and deletion)
+
+}